Added instruction combine to transform few more negative values addition to subtraction (Part 1)

This patch enables transforms for following patterns.
  (x + (~(y & c) + 1)   -->   x - (y & c)
  (x + (~((y >> z) & c) + 1)   -->   x - ((y>>z) & c)

Differential Revision: http://reviews.llvm.org/D3733

llvm-svn: 211266