Remove #define _BITSIZE 32.

I've no idea what _BITSIZE was supposed to be, glibc doesn't have it,
the BSDs don't have it, and no code is currently using it. But having
it set unconditionally to 32 sounds like a bad idea.

Change-Id: I900235c1489afba891fff0bc3b43e9d593249a4f
diff --git a/libc/include/stdint.h b/libc/include/stdint.h
index c795893..6e2f311 100644
--- a/libc/include/stdint.h
+++ b/libc/include/stdint.h
@@ -256,8 +256,6 @@
 #  define WINT_MIN INT32_MIN
 #endif
 
-#define _BITSIZE 32
-
 /* Keep the kernel from trying to define these types... */
 #define __BIT_TYPES_DEFINED__