Redefine the access bits to be compatible with other systems (#210)

Normally bits like this would be considered implementation details, but
in this case, `X_OK`, `W_OK`, and `R_OK` line up with `S_IXOTH`,
`S_IWOTH`, and `S_IROTH` on other systems, and those bits do have
well-known values.

expected/wasm32-wasi/predefined-macros.txt

@@ -397,7 +397,7 @@
 #define F_GETFD (1)
 #define F_GETFL (3)
 #define F_LOCK 1
-#define F_OK 0
+#define F_OK (0)
 #define F_SETFD (2)
 #define F_SETFL (4)
 #define F_TEST 3
@@ -1464,7 +1464,7 @@
 #define RS_HIPRI 0x01
 #define RUSAGE_CHILDREN 2
 #define RUSAGE_SELF 1
-#define R_OK 1
+#define R_OK (4)
 #define SARMAG 8
 #define SB 250
 #define SCHAR_MAX 127
@@ -1940,8 +1940,8 @@
 #define WONT 252
 #define WORD_BIT 32
 #define WRQ 02
-#define W_OK 2
-#define X_OK 4
+#define W_OK (2)
+#define X_OK (1)
 #define YESEXPR 0x50000
 #define YESSTR 0x50002
 #define YXDOMAIN ns_r_yxdomain

libc-bottom-half/headers/public/__header_unistd.h

@@ -5,10 +5,10 @@ struct stat;
 
 #include <__seek.h>
 
-#define F_OK 0
-#define R_OK 1
-#define W_OK 2
-#define X_OK 4
+#define F_OK (0)
+#define X_OK (1)
+#define W_OK (2)
+#define R_OK (4)
 
 #ifdef __cplusplus
 extern "C" {