Expand all leading tabs in markdown files

Given how problematic leading tabs in markdown files can be,
we have expanded all leading tabs in markdown files by:

```sh
find * -type f -name '*.md' -print |
  while read -r file; do
    rm -f "$file.tmp" ;
    expand < "$file" > "$file.tmp" ;
    mv -f -v "$file.tmp" "$file" ;
  done
```

Given the previous changes to `bin/pandoc-wrapper.sh` and other recent
commits and recent pull requests, the were were **NO** changes to
any HTML files.  This is a **good thing** as the expression goes.

No there are no leading tabs in any markdown files.
A check to catch any re-introduction of leading tabs
into any markdown file is on the way.

BTW: We do not have anything against leading tabs in files,
even though we have had to deal with their impact on forming
HTML from markdown files (as well as the calc source code).
It is just that this is one of those cases where tabs conflict
(sometimes caused by people wanting to change the classic
8-space tab model) with a desired outcome.

Perform `make www` to perform the above and test under macOS.

1994/README.md

@@ -60,7 +60,7 @@ Any of the following, though not required, would be a plus:
 If you think this may be you, send an email before 31 Dec 1995, to:
 
 ```
-    judges@toad.com		(use the Subject: 3rd judge)
+    judges@toad.com             (use the Subject: 3rd judge)
 ```
 
 Include in your message:
@@ -82,7 +82,7 @@ access to put up some IOCCC html pages, please send an email (say prior
 to 31 Dec 1995) to:
 
 ```
-    judges@toad.com		(use the Subject: www site)
+    judges@toad.com             (use the Subject: www site)
 ```
 
 describing your site and any other appropriate comments.  Thanks!

1994/horton/README.md

@@ -90,7 +90,7 @@ For more information, see my article
 [Using GraphTab; USENIX ;login: Sept/Oct 1992, pages 28-31](login_sept92-pp28-31.pdf).
 
 ```
-  	  MMMM,M,MM"MM,,,
+          MMMM,M,MM"MM,,,
          ,,MMMMMMMMM"""""""",
         ,MMMMM"""            ",
        ,MMM"                   "
@@ -106,7 +106,7 @@ For more information, see my article
         ",," , " "MMMMMMMM "   , "
          ,M , ""M,MMMMMMMM,M " ,,
          ,MM, MMMMMMMMMMMMMM,", M,
-  	M,M,MM"M"M" """M"MM,M M
+        M,M,MM"M"M" """M"MM,M M
          ,MMMMMM M,MMMMM"M MM""M
         M MMMMMM,M M"M"" M MMMM", ,
          "M"MMMMMMMMMM"M ,MMMMM M  ,,

1994/shapiro/README.md

@@ -63,7 +63,7 @@ The basic theme (pun) of this program is:
 
 ```
     "This time (everything) is not where it should be."
-	  ~~~~
+          ~~~~
 ```
 
 

1994/tvr/README.md

@@ -32,8 +32,8 @@ Mode may be a value from 0 to 12.
 ## Try:
 
 ``` <!---sh-->
-    ./try.color.sh		# for colour displays
-    ./try.bw.sh			# for Black & White displays
+    ./try.color.sh              # for colour displays
+    ./try.bw.sh                 # for Black & White displays
 ```
 
 
@@ -62,8 +62,8 @@ where `altmode` `1` - `4` correspond to mode `0` - `3` in the original entry and
 ### Alternate try:
 
 ``` <!---sh-->
-    ./try.alt.color.sh		# for colour displays
-    ./try.alt.bw.sh		# for Black & White displays
+    ./try.alt.color.sh          # for colour displays
+    ./try.alt.bw.sh             # for Black & White displays
 ```
 
 
@@ -169,15 +169,15 @@ compatible compiler (`gcc -ansi -pedantic` will do fine).
 This entry has been tested on wide variety of machines including:
 
 ```
-    Machine			OS
-    -------			--
-    Decstation 5000/240	Ultrix 4.3A
-    DECAlpha 3000/300	OSF/1 v1.3 and v2.0
-    IBM RS6000		AIX v3
-    SPARCStation IPX	SunOS 4.1.3
-    i486			Linux v1.1.8  (binarysize 3576 bytes
-					  using `gcc -O6 -s -N` ;)
-    HP 9000/730		HP-UX
+    Machine                     OS
+    -------                     --
+    Decstation 5000/240 Ultrix 4.3A
+    DECAlpha 3000/300   OSF/1 v1.3 and v2.0
+    IBM RS6000          AIX v3
+    SPARCStation IPX    SunOS 4.1.3
+    i486                        Linux v1.1.8  (binarysize 3576 bytes
+                                          using `gcc -O6 -s -N` ;)
+    HP 9000/730         HP-UX
 ```
 
 Also, many of the X server and X library versions have been tested and the
@@ -205,7 +205,7 @@ Well, obfuscated or not, some of the effects are very nice ;)
 Mandelbrot set is calculated from the formula
 
 ```
-  	 2
+         2
     Z   = Z  + Z
      n+1   n    0
 ```
@@ -213,7 +213,7 @@ Mandelbrot set is calculated from the formula
 and the Julia set is calculated from the formula
 
 ```
-  	 2
+         2
     Z   = Z  + C
      n+1   n
 ```