Add ISO 646 header (#168)

libc/isystem/iso646.h

@@ -0,0 +1,16 @@
+#ifndef COSMOPOLITAN_LIBC_ISYSTEM_ISO646_H_
+#define COSMOPOLITAN_LIBC_ISYSTEM_ISO646_H_
+
+#define and &&
+#define and_eq &=
+#define bitand &
+#define bitor |
+#define compl ~
+#define not !
+#define not_eq !=
+#define or ||
+#define or_eq |=
+#define xor ^
+#define xor_eq ^=
+
+#endif