R600/SI: Use VALU instructions for i1 ops
R600/SI: Only use SALU instructions for 64-bit add in a block of CF depth 0
R600/SI: Fix a bug with handling of INSERT_SUBREG in SIFixSGPRCopies

This prevents a future commit from regressing the load-i1.ll test.
R600/SI: Stop using VSrc_* as the default register class for types.

We now use SReg_* for integer types and VReg_* for floating-point types.
This should help simplify the SIFixSGPRCopies pass and no longer causes
ISel to insert a COPY after termiator instuctions that output a value.

This change is covered by exisitng tests.
[ASan/Win tests] Add more DLL tests: malloc & friends