[NTVDM]: Commit some local changes that can be committed now:

[NTVDM]: Commit some local changes that can be committed now:
- Whitespace fixes.
- Improve some DPRINTs.
- hardcoded_values--;
- Fix DisplayMessage() for NULL-terminated strings.
- Free the allocated block of memory in the mouse driver cleanup procedure.
- Properly inherit the parent process environment block if needed.
- Return the correct last error if DosCopyEnvironmentBlock fails.
- Big ifs turned into switch.
- Implement some INT 2Fh DOS multiplex functions (AX=1200h "Installation check", AX=1203h "Get DOS data segment", AX=1214h "Compare FAR pointers", AX=122Fh "Set DOS version to return"); remove the DPRINT for AX=1680h "Release Current Virtual Machine Time-slice".
- Stubplement INT 2Ah "DOS critical sections / network" (it just monitors calls to itself at the moment).
- Use the boot drive root path as the current directory if we failed retrieving a valid one.
- Offsetize the DOS_SYSVARS members (so that I don't have to compute by head the offsets, especially when some of the members is a structure from which I don't know in advance its size); add some C_ASSERTs on the size of DOS standard structures.
- Move the NullDriverRoutine buffer outside the sysvars buffer (because it has nothing to do inside it).
- In ConDrvReadInput: do not echo the first part of an extended character.
- Add basic support for changing the reported DosVersion.

svn path=/trunk/; revision=68395