Fix a few -pedantic warnings

We're not enabling -pedantic by default, but a quick test brought up a few
issues that we should fix.

shared/config-parser.h

@@ -57,7 +57,7 @@ enum weston_option_type {
 	WESTON_OPTION_INTEGER,
 	WESTON_OPTION_UNSIGNED_INTEGER,
 	WESTON_OPTION_STRING,
-	WESTON_OPTION_BOOLEAN,
+	WESTON_OPTION_BOOLEAN
 };
 
 struct weston_option {

shared/image-loader.c

@@ -334,7 +334,7 @@ load_webp(FILE *fp)
 
 
 struct image_loader {
-	char header[4];
+	unsigned char header[4];
 	int header_size;
 	pixman_image_t *(*load)(FILE *fp);
 };