syntax: Use STREQ/STRNEQ in place of strcmp.

Found by 'make syntax-check'.

generator/perl.ml

@@ -47,6 +47,8 @@ let rec generate_perl_xs () =
 
 #include <guestfs.h>
 
+#define STREQ(a,b) (strcmp((a),(b)) == 0)
+
 static SV *
 my_newSVll(long long val) {
 #ifdef USE_64_BIT_ALL
@@ -434,7 +436,7 @@ user_cancel (g)
           fun argt ->
             let n = name_of_optargt argt in
             let uc_n = String.uppercase n in
-            pr "if (strcmp (this_arg, \"%s\") == 0) {\n" n;
+            pr "if (STREQ (this_arg, \"%s\")) {\n" n;
             (match argt with
              | OBool _
              | OInt _ ->

src/inspect-fs-unix.c

@@ -1067,7 +1067,7 @@ mdadm_app_cmp(const void *x, const void *y)
   const mdadm_app *a = x;
   const mdadm_app *b = y;
 
-  return strcmp(a->mdadm, b->mdadm) == 0;
+  return STREQ (a->mdadm, b->mdadm);
 }
 
 static void

tests/regressions/rhbz790721.c

@@ -184,7 +184,7 @@ start_thread (void *vi)
    * building code which is what this regression test is designed to
    * spot.
    */
-  if (strcmp (error, "child process died unexpectedly") != 0) {
+  if (STRNEQ (error, "child process died unexpectedly")) {
     fprintf (stderr, "rhbz790721: [thread %d]: error: %s\n", thread_id, error);
     *(int *)vi = -1;
     pthread_exit (vi);