Fix bugs in 1990/theorem

In this case these were not features.

The most important bug fix actually prevented the entry from working
properly: the generated code for the Fibonacci sequence just printed 0
over and over again. Added a segfault prevention here as it seemed like
if I'm going to fix it I might as well fix it properly. Removed this bug
from bugs.md.

A set of possible issues with the char m[][] array was also including
the size limit in the fgets() calls (that was my fault due to missing
the proper type of m at the time). Still might be good to test with
longer lines of input. Commands with known output are correct
nonetheless.

The other bug was due to the gets() to fgets() change where blank lines
were added where they shouldn't be. Now one can do ls | ./sorter and get
no blank lines after each file in the listing.

bugs.md

@@ -476,11 +476,6 @@ so it should stay with this note.
 this entry that prevented it from working. However if not enough args are
 specified this program will crash.  This should NOT be fixed.
 
-## STATUS: known bug - please help us fix
-
-On the other hand the `fibonacci` program that is generated prints a string of
-0s over and over again. Can you fix this? See the README.md for details on how
-to generate it.
 
 # 1991