[optimizing] Add support for x86 constant area

Use the Quick trick of finding the address of the method by calling the
next instruction and popping the return address into a register.  This
trick is used because of the lack of PC-relative addressing in 32 bit
mode on the X86.

Add a HX86ComputeBaseMethodAddress instruction to trigger generation
of the method address, which is referenced by instructions needing
access to the constant area.

Add a HX86LoadFromConstantTable instruction that takes a
HX86ComputeBaseMethodAddress and a HConstant that will be used to load
the value when needed.

Change Add/Sub/Mul/Div to detect a HX86LoadFromConstantTable right hand
side, and generate code that directly references the constant area.
Other uses will be added later.

Change the inputs to HReturn and HInvoke(s), replacing the FP constants
with HX86LoadFromConstantTable instead.  This allows values to be
loaded from the constant area into the right location.

Port the X86_64 assembler constant area handling to the X86.

Use the new per-backend optimization framework to do this conversion.

Change-Id: I6d235a72238262e4f9ec0f3c88319a187f865932
Signed-off-by: Mark Mendell <mark.p.mendell@intel.com>