Log Message:
Update to xproto-7.0.16. Changes:

Improves compatibility with some current OS'es, at the cost of
decreased compatibility with premillennial OS'es and pre-C89 compilers.

Death to RCS tags.
Remove all trace of X_NOT_STDC_ENV (#6527)
Remove a bunch of garbage for unsupported platforms.
__STDC__ is always defined in C89.
Use ## catenation not /**/
Remove #ifdef macII code left over from ancient A/UX 3.0 support
Removing dangling #else block from X_NOT_STDC_ENV removal
Use indentation to provide a map through the twisty maze of ifdefs, all alike
Drop support for SunOS 4 and Solaris releases older than 2.5 (1995)
Get rid of unneeded && clause in list of LP64 ifdefs in Xmd.h
Drop #ifdef USG checks for some truly ancient (pre-SVR4) SysV's
Don't need an #ifdef when both cases just include the same file
xproto 7.0.16
Apple: Only define _DARWIN_C_SOURCE if it isn't already defined
Cygwin/X: Don't destroy min/max macros in Xwindows.h
Restore macro definition of sleep(), needed by Xming