clean up vmem.h, remove unused instrumentation hooks
Removed virtual. Removed dyn loading msvcrt.dll and function pointers.
Replaced with Compiler's native CRT's malloc. Moved the CS parts
into _USE_LINKED_LIST blocks. There is nothing to protect if we aren't
putting headers on. Faster startup time is the result of this commit.
Before .text be8df .rdata 21171, after .text be88f .rdata 21121. I did
turn off _USE_LINKED_LIST as an experiment, it compiled successfully and
passed the /t/op/*.t tests (only ones I performed). I did not try the Knuth
stuff. See also this msg by Jan Dubois
https://rt.perl.org/rt3/Ticket/Display.html?id=88840#txn-1144384