Add fgets_a(), and use it instead of its pattern

[alejandro-colomar]

Cc: @kees

---

Revisions:

v1b

• Rebase

$ git rd 
1:  010f20f53 = 1:  15e0d871f lib/, src/: Use countof() instead of sizeof() with fgets(3)
2:  e04a90503 = 2:  d986b5e82 lib/fields.c: change_field(): Use a VLA
3:  3a95ddaed ! 3:  a6444d771 lib/: Use countof() instead of hardcoded lengths
    @@ lib/limits.c
      #include "string/strcmp/strprefix.h"
     @@ lib/limits.c: static int setup_user_limits (const char *uname)
         *
    -    * FIXME: A better (smarter) checking should be done
    +    * FIXME: a better (smarter) checking should be done
         */
     -  while (fgets (buf, 1024, fil) != NULL) {
     +  while (fgets(buf, countof(buf), fil) != NULL) {
4:  e46110570 = 4:  a5f2be58d lib/io/: fgets_a(): Add macro
5:  6cff3df10 ! 5:  9ad8d91f4 lib/, src/: Use fgets_a() instead of its pattern
    @@ lib/limits.c
      #include "string/strcmp/strprefix.h"
     @@ lib/limits.c: static int setup_user_limits (const char *uname)
         *
    -    * FIXME: A better (smarter) checking should be done
    +    * FIXME: a better (smarter) checking should be done
         */
     -  while (fgets(buf, countof(buf), fil) != NULL) {
     +  while (fgets_a(buf, fil) != NULL) {