Alphabetize forward declarations
Use helper function
Fix missing words in sentence
R600: Rename AMDIL file
R600/SI: Move selection of i64 add to separate function.

Also don't use a SmallVector for fixed size array.
R600/SI: Handle i64 sub.

We can handle it the same way as add
R600: Don't set fp_round_inreg action.

There's no point in setting this since it seems to only
by created in 1 place for ppcf128
R600: Move more out of AMDILISelLowering
R600: Move add/sub with overflow out of AMDILISelLowering

Add more tests for these.
R600: Select is not expensive.
R600: Remove AMDILISelLowering