gst/festival/gstfestival.c: Guard unistd.h with HAVE_UNISTD_H

gst/festival/gstfestival.c: Guard unistd.h with HAVE_UNISTD_H

Original commit message from CVS:
* gst/festival/gstfestival.c:
Guard unistd.h with HAVE_UNISTD_H
* gst/modplug/libmodplug/load_it.cpp:
* gst/modplug/libmodplug/sndfile.cpp:
* gst/modplug/libmodplug/sndfile.h:
* gst/modplug/libmodplug/stdafx.h:
Support for compiling with MSVC: use _MSC_VER for detecting MSVC instead
of MSC_VER. Make CanPackSamples take the type it's passed. Change scope
of a variable in load_it.cpp to MSVC's scoping rules.
* gst/sdp/gstsdpdemux.c:
Guard unistd.h with HAVE_UNISTD_H
Fixes #544457.