Cygwin: create separate bits/byteswap.h

Match glibc behaviour to expose the public bswap_* macros only with an
explicity #include <byteswap.h>; #include'ing <endian.h> should not expose
them.

Signed-off-by: Yaakov Selkowitz <yselkowi@redhat.com>

winsup/cygwin/include/bits/byteswap.h

@@ -0,0 +1,37 @@
+/* bits/byteswap.h
+
+This file is part of Cygwin.
+
+This software is a copyrighted work licensed under the terms of the
+Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
+details. */
+
+#ifndef _BITS_BYTESWAP_H
+#define _BITS_BYTESWAP_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+static __inline unsigned short
+__bswap_16 (unsigned short __x)
+{
+  return (__x >> 8) | (__x << 8);
+}
+
+static __inline unsigned int
+__bswap_32 (unsigned int __x)
+{
+  return (__bswap_16 (__x & 0xffff) << 16) | (__bswap_16 (__x >> 16));
+}
+
+static __inline unsigned long long
+__bswap_64 (unsigned long long __x)
+{
+  return (((unsigned long long) __bswap_32 (__x & 0xffffffffull)) << 32) | (__bswap_32 (__x >> 32));
+}
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* _BITS_BYTESWAP_H */