DBGF,DBGC: Added dmesg command and implemented it for linux guests.

DBGF,DBGC,++: PVM -> PUVM. Some refactoring and cleanup as well.

VMM,Main,Debugger,REM: VM API cleanup, prefering PUVM over PVM so we can use real reference counting and not have the memory backing the VM structure disappear on us.

Doxygen.

VMM,++: Try fix the async reset, suspend and power-off problems in PDM wrt conflicting VMM requests. Split them into priority requests and normal requests. The priority requests can safely be processed when PDM is doing async state change waits, the normal ones cannot. (The problem I bumped into was a unmap-chunk request from PGM being processed during PDMR3Reset, causing a recursive VMMR3EmtRendezvous deadlock.)

VMM reorg: Moving the public include files from include/VBox to include/VBox/vmm.

VMM source reorg.