IMCC will now generate an error if the register type is unknown rather than just assign it a PMC register.
P reg types are pmc, object, or a valid classname. Use pmc or object for "generic" P register to defer type checking.
I think a few compilers will now be broken but the patches should be very simple to fix them.
Also allow sub names without _ prepended, and allow @ to start labels. Tweak the fixup code a bit to use flags rather than looking for _ in symbol name.
Added parser stubs for .global to grammar.
-Melvin
