Move PG_HEAP to defs.h

Makes it easier accessible

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Move small things in VMFrame to header for inlining

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Move GetFrame to header

- need some trickery to avoid circular dependency

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Avoid repeated read barriers

They do not seem to be necessary all the time, just once.

Signed-off-by: Stefan Marr <git@stefan-marr.de>