Get GNU GMP test suite fully passing

- Fix stdio fmemopen() buffer behaviors
- Fix scanf() to return EOF when appropriate
- Prefer fseek/ftell names over fseeko/ftello
- Ensure locale field is always set in the TIB
- Fix recent regression in vfprintf() return count
- Make %n directive in scanf() have standard behavior

libc/libc.mk

@@ -35,5 +35,4 @@ o/$(MODE)/libc:	o/$(MODE)/libc/calls		\
 		o/$(MODE)/libc/tinymath		\
 		o/$(MODE)/libc/vga		\
 		o/$(MODE)/libc/x		\
-		o/$(MODE)/libc/zipos		\
 		$(LIBC_CHECKS)