[Power9] Implement new vsx instructions: insert, extract, test data class, min/max...

[Power9] Implement new vsx instructions: insert, extract, test data class, min/max, reverse, permute, splat

This change implements the following vsx instructions:

- Scalar Insert/Extract
    xsiexpdp xsiexpqp xsxexpdp xsxsigdp xsxexpqp xsxsigqp

- Vector Insert/Extract
    xviexpdp xviexpsp xvxexpdp xvxexpsp xvxsigdp xvxsigsp
    xxextractuw xxinsertw

- Scalar/Vector Test Data Class
    xststdcdp xststdcsp xststdcqp
    xvtstdcdp xvtstdcsp

- Maximum/Minimum
    xsmaxcdp xsmaxjdp
    xsmincdp xsminjdp

- Vector Byte-Reverse/Permute/Splat
    xxbrd xxbrh xxbrq xxbrw
    xxperm xxpermr
    xxspltib

30 instructions

Thanks Nemanja for invaluable discussion! Thanks Kit's great help!
Reviewers: hal, nemanja, kbarton, tjablin, amehsan

http://reviews.llvm.org/D16842

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@264567 91177308-0d34-0410-b5e6-96231b3b80d8