Reduce warnings/errors in libpayload when using picky compiler options

The new build system uses quite a few more -W flags for the compiler by
default than the old one. And that's for the better.

Change-Id: Ia8e3d28fb35c56760c2bd0983046c7067e8c5dd6
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/72
Tested-by: build bot (Jenkins)
Reviewed-by: Uwe Hermann <uwe@hermann-uwe.de>

payloads/libpayload/libc/getopt_long.c

@@ -57,10 +57,8 @@
 #include <libpayload.h>
 #include <getopt.h>
 #define warnx(x...) printf(x)
-/*
 #include <stdlib.h>
 #include <string.h>
-*/
 #define	REPLACE_GETOPT		/* use this getopt as the system getopt(3) */
 
 #ifdef REPLACE_GETOPT
@@ -84,7 +82,7 @@ int posixly_correct = 0;
 #define	BADARG		((*options == ':') ? (int)':' : (int)'?')
 #define	INORDER 	(int)1
 
-#define	EMSG		""
+#define	EMSG		(char*)""
 
 static int getopt_internal(int, char * const *, const char *,
 			   const struct option *, int *, int);