win32: fix argumentless sleep()

win32: fix argumentless sleep()

Before this commit, pause() was implemented as a macro calling
win32_sleep((32767L << 16) + 32767), which was causing the following
problems with argumentless sleep():

- it was sleeping for 4262198 seconds (~50 days) instead of forever
- it was triggering "sleep(2147450879) too large" warning

This commit implements pause() as a proper function which calls
win32_msgwait() with an INFINITE timeout.

[perl #133376]