regex: Fix cast error on VC2015 x64

`long` is 32 bits on 64-bit VC, so casting a pointer to `long` causes a
warning on VC2015 x64 and it becomes an error by the `/WX` flag.
This fixes the casting errors by using `intptr_t`.

Old MinGW needs to include `stdint.h` to use `intptr_t`.

gnu_regex/regcomp.c

@@ -2527,7 +2527,7 @@ parse_dup_op (bin_tree_t *elem, re_string_t *regexp, re_dfa_t *dfa,
     old_tree = NULL;
 
   if (elem->token.type == SUBEXP)
-    postorder (elem, mark_opt_subexp, (void *) (long) elem->token.opr.idx);
+    postorder (elem, mark_opt_subexp, (void *) (intptr_t) elem->token.opr.idx);
 
   tree = create_tree (dfa, elem, NULL, (end == -1 ? OP_DUP_ASTERISK : OP_ALT));
   if (BE (tree == NULL, 0))
@@ -3740,7 +3740,7 @@ create_token_tree (re_dfa_t *dfa, bin_tree_t *left, bin_tree_t *right,
 static reg_errcode_t
 mark_opt_subexp (void *extra, bin_tree_t *node)
 {
-  int idx = (int) (long) extra;
+  int idx = (int) (intptr_t) extra;
   if (node->token.type == SUBEXP && node->token.opr.idx == idx)
     node->token.opt_subexp = 1;
 

mk_mingw.mak

@@ -2,7 +2,7 @@
 
 include source.mak
 
-REGEX_DEFINES = -DHAVE_REGCOMP -D__USE_GNU -DHAVE_STDBOOL_H -Dstrcasecmp=stricmp
+REGEX_DEFINES = -DHAVE_REGCOMP -D__USE_GNU -DHAVE_STDBOOL_H -DHAVE_STDINT_H -Dstrcasecmp=stricmp
 
 CFLAGS = -Wall -std=gnu99
 # sizeof (size_t) == sizeof(unsigned long) == 4 on i686-w64-mingw32-gcc.