mingw: declare main()'s argv as const

In 84d32bf (sparse: Fix mingw_main() argument number/type errors,
2013-04-27), we addressed problems identified by the 'sparse' tool where
argv was declared inconsistently. The way we addressed it was by casting
from the non-const version to the const-version.

This patch is long overdue, fixing compat/mingw.h's declaration to
make the "argv" parameter const.  This also allows us to lose the
"const" trickery introduced earlier to common-main.c:main().

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

common-main.c

@@ -22,14 +22,8 @@ static void restore_sigpipe_to_default(void)
 	signal(SIGPIPE, SIG_DFL);
 }
 
-int main(int argc, char **av)
+int main(int argc, const char **argv)
 {
-	/*
-	 * This const trickery is explained in
-	 * 84d32bf7678259c08406571cd6ce4b7a6724dcba
-	 */
-	const char **argv = (const char **)av;
-
 	/*
 	 * Always open file descriptors 0/1/2 to avoid clobbering files
 	 * in die().  It also avoids messing up when the pipes are dup'ed

compat/mingw.h

@@ -535,7 +535,7 @@ extern CRITICAL_SECTION pinfo_cs;
 void mingw_startup();
 #define main(c,v) dummy_decl_mingw_main(); \
 static int mingw_main(c,v); \
-int main(int argc, char **argv) \
+int main(int argc, const char **argv) \
 { \
 	mingw_startup(); \
 	return mingw_main(__argc, (void *)__argv); \