The inliner has traditionally not considered call sites

that appear due to inlining a callee as candidates for
futher inlining, but a recent patch made it do this if
those call sites were indirect and became direct.

Unfortunately, in bizarre cases (see testcase) doing this
can cause us to infinitely inline mutually recursive
functions into callers not in the cycle.  Fix this by
keeping track of the inline history from which callsite
inline candidates got inlined from.

This shouldn't affect any "real world" code, but is required
for a follow on patch that is coming up next.

llvm-svn: 102822