Avoid uninitialized-variable warnings from older compilers.

Avoid uninitialized-variable warnings from older compilers.

Some of the buildfarm is still unhappy with WinGetFuncArgInPartition
even after 2273fa32b.  While it seems to be just very old compilers,
we can suppress the warnings and arguably make the code more readable
by not initializing these variables till closer to where they are
used.  While at it, make a couple of cosmetic comment improvements.