Remove swap16/swap32/swap64 header pollution.

This seems to be obsolete BSD stuff, and the only references to it in the
tree are people #undef'ing it.

Bug: http://b/2735009
Change-Id: Icde523ae2d15cf1025357d861f97b415e89e4f9a
diff --git a/libc/include/byteswap.h b/libc/include/byteswap.h
index 74b0e91..628fb7f 100644
--- a/libc/include/byteswap.h
+++ b/libc/include/byteswap.h
@@ -28,11 +28,10 @@
 #ifndef _BYTESWAP_H_
 #define _BYTESWAP_H_
 
-/* endian.h rather than sys/endian.h so we get the machine-specific file. */
-#include <endian.h>
+#include <sys/endian.h>
 
-#define  bswap_16(x)   swap16(x)
-#define  bswap_32(x)   swap32(x)
-#define  bswap_64(x)   swap64(x)
+#define bswap_16(x) __swap16(x)
+#define bswap_32(x) __swap32(x)
+#define bswap_64(x) __swap64(x)
 
 #endif /* _BYTESWAP_H_ */