refactor: iwyu (#26062)

src/nvim/regexp.c

@@ -7,9 +7,11 @@
 // #define REGEXP_DEBUG
 
 #include <assert.h>
+#include <ctype.h>
 #include <inttypes.h>
 #include <limits.h>
 #include <stdbool.h>
+#include <stddef.h>
 #include <string.h>
 #include <sys/types.h>
 
@@ -22,6 +24,7 @@
 #include "nvim/garray.h"
 #include "nvim/gettext.h"
 #include "nvim/globals.h"
+#include "nvim/grid_defs.h"
 #include "nvim/keycodes.h"
 #include "nvim/macros.h"
 #include "nvim/mark.h"