Handle long delay between video frames in multi-thread decoder(issue 312)

Handle long delay between video frames in multi-thread decoder(issue 312)

This is reported by m...@hesotech.de (see issue 312):
"The decoder causes an access violation
when you decode the first frame, then make a pause of about
60 seconds and then decode further frames. But only if
vpx_codec_dec_cfg_t.threads> 1.

This is caused by a timeout of WaitForSingleObject.
When I change the definition of VPXINFINITE to INFINITE(0xFFFFFFFF),
the problem is solved."

Reproduced the crash and verified the changes on Windows platform.
This brings the behavior inline with the other platforms using sem_wait().

Change-Id: I27b32f90bce05846ef2684b50f7a88f292299da1