Currently the code uses gzFile * for a zlib file descriptor, which

is not correct.  The code works by accident because gzFile is
currently defined as void *, and internally it would be casted from
or to its real type.

A newer version of zlib will instead define it as a pointer to a
specific type pointer (namely, struct gzFile_s *).  This therefore
would cause stricter checks and compiler would catch this type
mismatch.

This change does not cause any changes to the resulting binary,
as validated with md5(1).

MFC after:	3 days

usr.bin/makewhatis/makewhatis.c

@@ -693,7 +693,7 @@ enum { STATE_UNKNOWN, STATE_MANSTYLE, STATE_MDOCNAME, STATE_MDOCDESC };
 static void
 process_page(struct page_info *page, char *section_dir)
 {
-	gzFile *in;
+	gzFile in;
 	char buffer[4096];
 	char *line;
 	StringList *names;