Add a comment about SimpleCoalescing.
Variables in the Cfg::Variables list will never be NULL.
Change -verbose option to --verbose for consistency.
Use snprintf() instead of sprintf().

Also, there is some in-progress work on improving the iteration
interface in IceLoweringContext.
Reformat.
assert.h --> cassert; stdio.h --> cstdio
Add some comments.
Put everything inside the Ice namespace.
IceCfgNode --> CfgNode
IceInst --> Inst
IceLive --> Live
IceOperand --> Operand
IceGlobalContext --> GlobalContext
IceVariable --> Variable
IceConstant --> Constant
IceTargetLowering --> TargetLowering
Ice<foo>List --> <foo>List
IceValueTranslation --> ValueTranslation
IceTypePool --> TypePool
IceRelocatableTuple --> RelocatableTuple