R600/SI: Remove promotion of instructions to e64 forms.

Instructions are now generally selected to the e64 forms originally,
and shrunk down later. Rename foldOperands to legalizeOperands,
since that's really most of what it tries to do.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217959 91177308-0d34-0410-b5e6-96231b3b80d8
LineIterator: Provide a variant that keeps blank lines

It isn't always useful to skip blank lines, as evidenced by the
somewhat awkward use of line_iterator in llvm-cov. This adds a knob to
control whether or not to skip blanks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217960 91177308-0d34-0410-b5e6-96231b3b80d8