dll_ver: don't call Wow64 stuff on 32-bit vista

+minor improvements:
. move libjpeg-specific stuff to its own header

This was SVN commit r5088.

source/lib/module_init.cpp

@@ -61,6 +61,7 @@ retry:
 		return false;
 	if(!cpu_CAS(pInitState, latchedInitState, latchedInitState-1))
 		goto retry;
+
 	// refcount reached zero => allow shutdown.
 	if(latchedInitState-1 == MODULE_UNINITIALIZED)
 		return true;