replace {pre,suf}fixcmp() with {starts,ends}_with()

Leaving only the function definitions and declarations so that any
new topic in flight can still make use of the old functions, replace
existing uses of the prefixcmp() and suffixcmp() with new API
functions.

The change can be recreated by mechanically applying this:

    $ git grep -l -e prefixcmp -e suffixcmp -- \*.c |
      grep -v strbuf\\.c |
      xargs perl -pi -e '
        s|!prefixcmp\(|starts_with\(|g;
        s|prefixcmp\(|!starts_with\(|g;
        s|!suffixcmp\(|ends_with\(|g;
        s|suffixcmp\(|!ends_with\(|g;
      '

on the result of preparatory changes in this series.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/bisect.c b/bisect.c
index 1e46a4f..37200b4 100644
--- a/bisect.c
+++ b/bisect.c
@@ -406,9 +406,9 @@
 	if (!strcmp(refname, "bad")) {
 		current_bad_sha1 = xmalloc(20);
 		hashcpy(current_bad_sha1, sha1);
-	} else if (!prefixcmp(refname, "good-")) {
+	} else if (starts_with(refname, "good-")) {
 		sha1_array_append(&good_revs, sha1);
-	} else if (!prefixcmp(refname, "skip-")) {
+	} else if (starts_with(refname, "skip-")) {
 		sha1_array_append(&skipped_revs, sha1);
 	}