Try to reduce the compile time impact of r161232.

Try to reduce the compile time impact of r161232.

The previous change caused fast isel to not attempt handling any calls to
builtin functions.  That included things like "printf" and caused some
noticable regressions in compile time.  I wanted to avoid having fast isel
keep a separate list of functions that had to be kept in sync with what the
code in SelectionDAGBuilder.cpp was handling.  I've resolved that here by
moving the list into TargetLibraryInfo.  This is somewhat redundant in
SelectionDAGBuilder but it will ensure that we keep things consistent.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161263 91177308-0d34-0410-b5e6-96231b3b80d8