posix: protect EOF being parsed as operator and 1

see 7d095c7453/dev-libs/jsoncpp/patches/jsoncpp-1.9.4.patchset

Change-Id: Iaedb67eb51e86cbc5b73a21a86b6b0b6b70209b0
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3679
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

headers/posix/libio.h

@@ -31,7 +31,7 @@
 #include <stdarg.h>
 
 #ifndef EOF
-#	define EOF -1
+#	define EOF (-1)
 #endif
 
 #define _IO_pos_t		off_t /* obsolete */

headers/posix/stdio.h

@@ -39,7 +39,7 @@
 #ifdef EOF
 #	undef EOF
 #endif
-#define EOF -1
+#define EOF (-1)
 
 #ifndef SEEK_SET
 #	define SEEK_SET 0