Add exp2f, sqrtf, fabsf to whitelist

bug 19425238

LLVM constant folding introduces call to unmangled math functions.  For
example, pow(2, x) becomes exp2(x).  These functions must be added to
our whitelist.

Change-Id: I5dcadafbc821faf3e98d4a7d2106c082c8c09f63
1 file changed