Imported from the LLVM compiler_rt library on master branch as of
30 Oct 2018 (SVN revision: r345645).

This is to get the __popcountsi2(si_int a) and __popcountdi2(di_int a)
builtin which are required by a driver that uses a __builtin_popcount().

Change-Id: I8e0d97cebdd90d224690c8ce1b02e657acdddb25
Signed-off-by: Lionel Debieve <lionel.debieve@st.com>