Fix compat/regex ANSIfication on MinGW

compat/regexec.c had a weird combination of function declaration in ANSI
style and function definition in K&R style, for example:

 static unsigned
 re_copy_regs (struct re_registers *regs, regmatch_t *pmatch,
      int nregs, int regs_allocated) internal_function;

 static unsigned
 re_copy_regs (regs, pmatch, nregs, regs_allocated)
     struct re_registers *regs;
     regmatch_t *pmatch;
     int nregs, regs_allocated;
 { ... }

with this #define:

 #ifndef _LIBC
 # ifdef __i386__
 #  define internal_function   __attribute ((regparm (3), stdcall))
 # else
 #  define internal_function
 # endif
 #endif

The original version as shown above was fine, but with the ANSIfied
function definition and in the case where internal_function is not empty,
gcc identifies the declaration and definition as different and bails out.

Adding internal_function to the definition doesn't help (it results in
a syntax error); hence, remove it from the subset of declarations that gcc
flags as erroneous.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/regex/regexec.c

@@ -40,20 +40,19 @@ static reg_errcode_t re_search_internal (const regex_t *preg,
 					 const char *string, int length,
 					 int start, int range, int stop,
 					 size_t nmatch, regmatch_t pmatch[],
-					 int eflags) internal_function;
+					 int eflags);
 static int re_search_2_stub (struct re_pattern_buffer *bufp,
 			     const char *string1, int length1,
 			     const char *string2, int length2,
 			     int start, int range, struct re_registers *regs,
-			     int stop, int ret_len) internal_function;
+			     int stop, int ret_len);
 static int re_search_stub (struct re_pattern_buffer *bufp,
 			   const char *string, int length, int start,
 			   int range, int stop, struct re_registers *regs,
-			   int ret_len) internal_function;
+			   int ret_len);
 static unsigned re_copy_regs (struct re_registers *regs, regmatch_t *pmatch,
-			      int nregs, int regs_allocated) internal_function;
-static reg_errcode_t prune_impossible_nodes (re_match_context_t *mctx)
-     internal_function;
+			      int nregs, int regs_allocated);
+static reg_errcode_t prune_impossible_nodes (re_match_context_t *mctx);
 static int check_matching (re_match_context_t *mctx, int fl_longest_match,
 			   int *p_match_first) internal_function;
 static int check_halt_state_context (const re_match_context_t *mctx,