Turns the results of these macros from compound to regular statements using the old `do { ... } while(0)` trick. Must have for function-like macros.

When the execution reaches the end of the main functions, they implicitly return a successful status.

iscntrl: Didn't handle the EOF macro correctly
isgraph: Didn't handle '~' (tilde) correctly
ispunct: Several issues

Wrote tests for the functions implemented in 40558b26 and maybe made that
test a little more comprehensible.

Also made sure that fmt.sh and test.sh were being executed by bash all
the time (compatibility with other shells).

Add ctype functions
  - isalnum
  - isalpha
  - isascii
  - isdigit
  - islower
  - isspace
  - isupper
Add stdlib functions
  - atoi
  - atol
Fix some warnings
Make a fmt run