Add support for phi nodes in the LLVM C API test

Summary: This required to add binding to Instruction::removeFromParent so that instruction can be forward declared and then moved at the right place.

Reviewers: bogner, chandlerc, echristo, dblaikie, joker.eph, Wallbraker

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D17057

llvm-svn: 260597