[IRCE][NFC] Rename IndVarNext to IndVarBase

Renaming as a preparation step to generalizing IRCE for comparison not only against
the next value of an indvar, but also against the current.

Differential Revision: https://reviews.llvm.org/D36509


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312215 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed