Add isl operator overloads for isl::pw_aff

Piecewise affine expressions have directly corresponding mathematical
operators. Introduce these operators as overloads as this makes writing
code with isl::pw_aff expressions more directly readable.

We can now write:

  A = B + C    instead of    A = B.add(C)

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@327216 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed