Review and fix regular expressions of the form /^foo|bar$/.
Replace regular expressions with simple string comparisons where
possible.
Use '(?:subregexp)' instead of '(subregexp)' wherever possible.
'dlls/gdi' does not have a win16drv subdirectory anymore so simplify
regular expressions accordingly.

diff --git a/tools/winapi_check/modules.pm b/tools/winapi_check/modules.pm
index 6f2b990..06121b9 100644
--- a/tools/winapi_check/modules.pm
+++ b/tools/winapi_check/modules.pm
@@ -71,7 +71,7 @@
 	/^$/ && next;
 
 	if($header)  {
-	    if(/^\d+|@/) { $header = 0; $lookahead = 1; }
+	    if(/^(?:\d+|@)/) { $header = 0; $lookahead = 1; }
 	    next;
 	}