llvm-svn: 75703

Begin the painful process of tearing apart the rat'ss nest that is Constants.cpp and ConstantFold.cpp.
This involves temporarily hard wiring some parts to use the global context.  This isn't ideal, but it's
the only way I could figure out to make this process vaguely incremental.

llvm-svn: 75445

llvm-svn: 71993

to make the copy constructor and destructor protected, and corresponding
adjustments to the unittests.

llvm-svn: 70644

the comparison operators were not only unnecessary in the presence of the
implicit conversion; they caused ambiguous overload errors. So I deleted them.

llvm-svn: 70243