Warning cleanup

- ignoring const
- declarations after statements
- some C files didnt include own headers (risking them getting out of sync)

Closes #1064

src/common/cfgfiles.c

@@ -1311,7 +1311,7 @@ cmd_set (struct session *sess, char *tbuf, char *word[], char *word_eol[])
 }
 
 int
-hexchat_open_file (char *file, int flags, int mode, int xof_flags)
+hexchat_open_file (const char *file, int flags, int mode, int xof_flags)
 {
 	char *buf;
 	int fd;