treewide: rename 'EXCL_FLAG_' to 'PATTERN_FLAG_'

The first consumer of pattern-matching filenames was the
.gitignore feature. In that context, storing a list of patterns
as a 'struct exclude_list'  makes sense. However, the
sparse-checkout feature then adopted these structures and methods,
but with the opposite meaning: these patterns match the files
that should be included!

It would be clearer to rename this entire library as a "pattern
matching" library, and the callers apply exclusion/inclusion
logic accordingly based on their needs.

This commit replaces 'EXCL_FLAG_' to 'PATTERN_FLAG_' in the
names of the flags used on 'struct path_pattern'.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/check-ignore.c b/builtin/check-ignore.c
index 97108cc..28b8f14 100644
--- a/builtin/check-ignore.c
+++ b/builtin/check-ignore.c
@@ -34,8 +34,8 @@ static const struct option check_ignore_options[] = {
 
 static void output_pattern(const char *path, struct path_pattern *pattern)
 {
-	char *bang  = (pattern && pattern->flags & EXC_FLAG_NEGATIVE)  ? "!" : "";
-	char *slash = (pattern && pattern->flags & EXC_FLAG_MUSTBEDIR) ? "/" : "";
+	char *bang  = (pattern && pattern->flags & PATTERN_FLAG_NEGATIVE)  ? "!" : "";
+	char *slash = (pattern && pattern->flags & PATTERN_FLAG_MUSTBEDIR) ? "/" : "";
 	if (!nul_term_line) {
 		if (!verbose) {
 			write_name_quoted(path, stdout, '\n');