Revisit 1990 entries

Although I previously got them to all compile they did not all work. Now
they do except that jaw does not work properly in macOS (I have noticed
something odd in linux too but it appears to work mostly if not
entirely).

Yusuke Endoh pointed out for 1990/theorem that atof() nowadays needs
include stdlib.h so this was added to the file. As well I added the
inclusion of string.h for strcmp(). I also fixed some segfaults in this
entry (even though the judges pointed out that for NULL pointer one
needs the four '0 0 0 0' it still segfaulted under those conditions) so
that everything should work now under both linux and macOS. There were
iirc two parts to this: one the NULL pointer is no longer dereferenced
but also the type being passed to strcmp() was a int * and not a char *.
This prevented 1990/theorem/sorter from working at all (segfault) and as
I recall it there was another segfault I encountered as well.

For 1990/jaw Yusuke Endoh provided a ruby implementation of btoa as it's
not always available in modern systems. Thank you Yusuke!

In 1990/jaw shark.sh had to be modified as well. This had to do with '.'
not being in the default PATH.

As well I had previously made a mistake about btoa versus atob as both
were referenced in 1990/jaw/README.md. I believe I have this correct
now.

Many if not all the README files were modified with various changes
including formatting (like turning them into markdown) and section
titles amongst other things.

I seem to recall I'm missing something here but I can't recall what I
recall :-) so this will have to suffice this time round (maybe it was
the btoa/atob issue that I just remembered and added above but I'm not
sure).

1990/dds/README.md

@@ -11,6 +11,9 @@
 	make all
 
 
+Modern compilers could not compile this entry but Yusuke Endoh supplied a patch
+which lets it compile. Thank you Yusuke!
+
 ### To run
 
 	./dds
@@ -19,31 +22,32 @@
 NOTE: this entry uses `gets()` so you might get a warning when compiling and
 running this entry.
 
+### Try:
 
-## Judges' comments
-
-    Give the following lines as input:
+Give the following lines as input:
     
 	OLD LANDER.BAS
 	RUN
 
-    Be sure not to run out of fuel!
+NOTE: this is case sensitive.
 
 
-    Modern compilers could not compile this entry but Yusuke Endoh supplied a patch
-    which lets it compile. Thank you Yusuke!
+## Judges' comments
+
+
+Be sure not to run out of fuel!
 
 
 ## Author's comments
 
-    This is the DDS-BASIC Interpreter (Version 1.00). 
+This is the DDS-BASIC Interpreter (Version 1.00). 
 
-    Immediate commands:
+Immediate commands:
 
 	RUN	LIST	NEW	OLD filename
 	BYE	SAVE filename
 
-    Program commands:
+Program commands:
 
 	variable names a to z		variables initialized to 0 on RUN
 	FOR var = exp TO exp		NEXT variable
@@ -53,7 +57,7 @@ running this entry.
 	PRINT exp			var = exp
 	REM any text			END
 
-    Expressions (ranked by precedence):
+Expressions (ranked by precedence):
 
 	Bracketed expressions
 	number (leading 0 for octal, 0x for hex, else decimal), variable
@@ -66,20 +70,21 @@ running this entry.
 	(* and + are also used for boolean AND and boolean OR)
 	Boolean expressions evaluate to 0 for false and 1 for true
 
-    Editing:
+Editing:
 
-	- Line editor using line re-entry.
-	- A line number with nothing following it, deletes the line.
+- Line editor using line re-entry.
+- A line number with nothing following it, deletes the line.
 
-    Input format:
+Input format:
 
-	- Free format positioning of tokens on the line.
-	- No space is allowed before the line number.
-	- Exactly one space is needed between the OLD or SAVE command and 
-	  the filename.
-	- ALL INPUT MUST BE UPPERCASE.
+- Free format positioning of tokens on the line.
+- No space is allowed before the line number.
+- Exactly one space is needed between the OLD or SAVE command and 
+  the filename.
+- ALL INPUT MUST BE UPPERCASE.
 
-    Limits:
+
+Limits:
 
 	Line numbers		1-10000
 	Line length		999 characters
@@ -89,26 +94,28 @@ running this entry.
 	Expressions		-32768 - 32767 for 16 bit machines, 
 				-2147483648 - 2147483647 for 32 bit machines
 
-    Error checking / error reports:
+Error checking / error reports:
 
-	No error checking is performed.
-	The message `core dumped' signifies a syntax or semantic error.
 
-    Hosting Environment:
+No error checking is performed.
+It might dump core if a syntax or semantic error is encountered.
+
+
+Hosting Environment:
 
 	ANSI C, traditional K&R C or OSF ANDF
 	ASCII or EBCIDIC character set
 	48K bytes memory
 
-    The Speed of DDS-BASIC Interpreter (Version 1.00). relative to
-    Microsoft Advanced BASIC 3.31 is Approximately 60%.
+The Speed of DDS-BASIC Interpreter (Version 1.00). relative to
+Microsoft Advanced BASIC 3.31 is Approximately 60%.
 
-    The code size could be further reduced by doing ugly things like
-    not declaring the return type of functions, not freeing memory,
-    #defining define, and joining lines.  In its present 1536 character
-    form the program is reasonably portable (it may fail to run in a
-    tagged object architecture) and nicely formatted (it fits in an
-    80*25 screen).
+The code size could be further reduced by doing ugly things like
+not declaring the return type of functions, not freeing memory,
+#defining define, and joining lines.  In its present 1536 character
+form the program is reasonably portable (it may fail to run in a
+tagged object architecture) and nicely formatted (it fits in an
+80*25 screen).
 
 Copyright (c) 1990, Landon Curt Noll & Larry Bassel.
 All Rights Reserved.  Permission for personal, educational or non-profit use is