Major registor allocation rework - stage 1.

Major registor allocation rework - stage 1.

Direct usage of registers abstracted out.
Live values tracked locally.  Redundant loads and stores suppressed.
Address of registers and register pairs unified w/ single "location" mechanism
Register types inferred using existing dataflow analysis pass.
Interim (i.e. Hack) mechanism for storing register liveness info. Rewrite TBD.
Stubbed-out code for linear scan allocation (for loop and long traces)
Moved optimistic lock check for monitor-enter/exit inline for Thumb2
Minor restructuring, renaming and general cleanup of codegen
Renaming of enums to follow coding convention
Formatting fixes introduced by the enum renaming

Rewrite of RallocUtil.c and addition of linear scan to come in stage 2.