maint: prefer STREQ_LEN and STRPREFIX over strncmp in all cases

* cfg.mk (sc_prohibit_strncmp): Improve the search pattern: use
_sc_search_regexp to find all invocations of strncmp except when
used on a macro definition line; just match the function name with
an opening parenthesis.  Before, the expression missed places where
the comparison against 0 was in a subsequent line.
* src/system.h (STRNCMP_LIT): Shorten 'literal' to 'lit' to move
the whole definition of the macro into one line - thus making
sc_prohibit_strncmp pass.
(STRPREFIX): Add space before parenthesis.
* src/du.c (main): Prefer STREQ_LEN over strncmp.
* src/pinky.c (scan_entries): Likewise.
* src/tac.c (tac_seekable): Likewise.
* src/who.c (scan_entries): Likewise.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/tac.c b/src/tac.c
index 9fce47208..b69953f35 100644
--- a/src/tac.c
+++ b/src/tac.c
@@ -296,8 +296,8 @@ tac_seekable (int input_fd, const char *file, off_t file_pos)
         {
           /* 'match_length' is constant for non-regexp boundaries. */
           while (*--match_start != first_char
-                 || (match_length1 && strncmp (match_start + 1, separator1,
-                                               match_length1)))
+                 || (match_length1 && !STREQ_LEN (match_start + 1, separator1,
+                                                  match_length1)))
             /* Do nothing. */ ;
         }