Add more Project Euler goodies
Add sample mazes with solutions
Minor edit: update comments, small detail changes

return 1 -> return EXIT_FAILURE
 #define true ~0 -> #define true 1
Use enum instead of 'const char foo'

Also add disclaimer
Make separate function for string comparisons

Because !strcmp(foostring, barstring) is too opaque
Add better color configuration support
Check for NULL edge case

"Edge case" in a literal sense since it happens when you try to "get" a cell
not within the dimensions of the maze.
Perform dead-end fills immediately without looping

Major performance upgrade. Instead of making repeated iterations over the maze
until there are no more dead ends to fill, this commit makes the program fill
the entire dead end as soon as it's found. So repeatededly looping over the
entire maze is no longer needed!
Minor edit: remove leading newline in output
Minor edit: add #undefs to match the #defines