Add a new method to create SimpleInliner instance and make pre-inliner use this.

This adds a createFunctionInliningPass pass that takes an InlineParams object and use this to create the pre-inliner pass. This prevents the regular inliner's threshold flag from influencing the preinliner.

Differential revision: https://reviews.llvm.org/D23377

llvm-svn: 278377