Fix a few pointless compiler warnings on Windows

+ The HAVE_DECL macros are 0 or 1, not defined or undefined
+ The argv pointers shouldn't be const; getopt_long rearranges them
Index: patch-2.6.1-2-g2c4e3ec/gl/lib/strndup.c
===================================================================
--- patch-2.6.1-2-g2c4e3ec.orig/gl/lib/strndup.c	2010-01-03 00:11:40.000000000 +0000
+++ patch-2.6.1-2-g2c4e3ec/gl/lib/strndup.c	2010-01-03 00:13:02.000000000 +0000
@@ -23,7 +23,7 @@
 
 #include <stdlib.h>
 
-#ifndef HAVE_DECL_STRNLEN
+#if !HAVE_DECL_STRNLEN
 extern size_t strnlen (const char *, size_t);
 #endif
 
Index: patch-2.6.1-2-g2c4e3ec/gl/lib/xstrndup.c
===================================================================
--- patch-2.6.1-2-g2c4e3ec.orig/gl/lib/xstrndup.c	2010-01-03 00:11:30.000000000 +0000
+++ patch-2.6.1-2-g2c4e3ec/gl/lib/xstrndup.c	2010-01-03 00:12:52.000000000 +0000
@@ -23,7 +23,7 @@
 #include <string.h>
 #include "xalloc.h"
 
-#ifndef HAVE_DECL_STRNDUP
+#if !HAVE_DECL_STRNDUP
 extern char *strndup (const char *, size_t);
 #endif
 
Index: patch-2.6.1-2-g2c4e3ec/src/patch.c
===================================================================
--- patch-2.6.1-2-g2c4e3ec.orig/src/patch.c	2010-01-03 00:34:42.000000000 +0000
+++ patch-2.6.1-2-g2c4e3ec/src/patch.c	2010-01-03 00:34:52.000000000 +0000
@@ -80,7 +80,7 @@ static char const else_defined[] = "\n#e
 static char const end_defined[] = "\n#endif\n";
 
 static int Argc;
-static char * const *Argv;
+static char **Argv;
 
 static FILE *rejfp;  /* reject file pointer */