Add some wrappers for usual loops around strsep(3)

[alejandro-colomar]

Suggested-by: @hallyn

---

Revisions:

v2

• Workaround two GCC bugs [@uecker]
  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118044
  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118043

$ git range-diff master gh/astrsep2ls astrsep2ls 
 1:  ad66293e !  1:  ccee0abc lib/string/strtok/: strsep2arr(), STRSEP2ARR(): Add APIs
    @@ lib/string/strtok/strsep2arr.h (new)
     +)
     +
     +
    -+ATTR_ACCESS(read_write, 1) ATTR_ACCESS(write_only, 4)
    ++ATTR_ACCESS(read_write, 1) ATTR_ACCESS(write_only, 4, 3)
     +ATTR_STRING(1) ATTR_STRING(2)
     +inline ssize_t strsep2arr(char *s, const char *restrict delim,
     +    size_t n, char *a[restrict n]);
 2:  5f98de6e !  2:  95f4a921 lib/string/strtok/: strsep2ls(), STRSEP2LS(): Add APIs
    @@ lib/string/strtok/strsep2ls.h (new)
     +#define STRSEP2LS(s, delim, ls)  strsep2ls(s, delim, NITEMS(ls), ls)
     +
     +
    -+ATTR_ACCESS(read_write, 1) ATTR_ACCESS(write_only, 4)
    ++ATTR_ACCESS(read_write, 1) ATTR_ACCESS(write_only, 4, 3)
     +ATTR_STRING(1) ATTR_STRING(2)
     +inline ssize_t strsep2ls(char *s, const char *restrict delim,
     +    size_t n, char *ls[restrict n]);
 3:  a5390a9c =  3:  ab168394 lib/: Use STRSEP2LS() instead of its pattern
 4:  4f29f5e7 =  4:  411dd0be lib/port.c: getportent(): Use STRSEP2ARR() instead of its pattern
 5:  519fc865 =  5:  dc232372 lib/: Use strsep2arr() instead of its pattern
 6:  57f481b4 =  6:  a2dd29c8 lib/: Use STRSEP2ARR() instead of its pattern
 7:  70f747cc =  7:  884f9611 lib/string/strtok/: astrsep2ls(): Add function
 8:  3b908118 =  8:  abcaf9ed lib/sgetgrent.c: list(): Explicitly free(3) at the start of the function
 9:  28366e31 =  9:  60a02867 lib/string/strtok/: xastrsep2ls(): Add function
10:  8b6cac14 = 10:  040a7acf lib/: Use xastrsep2ls() instead of its pattern

v2b

• Rebase

$ git range-diff alx/master..gh/astrsep2ls master..astrsep2ls 
 1:  ccee0abc =  1:  060db63c lib/string/strtok/: strsep2arr(), STRSEP2ARR(): Add APIs
 2:  95f4a921 =  2:  2858fb22 lib/string/strtok/: strsep2ls(), STRSEP2LS(): Add APIs
 3:  ab168394 =  3:  e2f2c2ed lib/: Use STRSEP2LS() instead of its pattern
 4:  411dd0be =  4:  a707b113 lib/port.c: getportent(): Use STRSEP2ARR() instead of its pattern
 5:  dc232372 =  5:  d7fdde21 lib/: Use strsep2arr() instead of its pattern
 6:  a2dd29c8 =  6:  b708da45 lib/: Use STRSEP2ARR() instead of its pattern
 7:  884f9611 =  7:  051e32e2 lib/string/strtok/: astrsep2ls(): Add function
 8:  abcaf9ed =  8:  9f3f560f lib/sgetgrent.c: list(): Explicitly free(3) at the start of the function
 9:  60a02867 =  9:  5f22734d lib/string/strtok/: xastrsep2ls(): Add function
10:  040a7acf = 10:  729949bd lib/: Use xastrsep2ls() instead of its pattern