1. Add sincos, sincosf, and sincosl to API >= 9 (for ARM only,
because X86 and MIPS have it already)
2. Add nan, nanf, nanl, and tgammaf to API >= 13 (11 actually,
but we don't want to add another API which is not released)
3. Add log2, log2f, log2l, logbl, nexttoward, and nexttowardl to
API >= 18
See b.android.com/38423
Change-Id: I0a756aeeddafc3862f3c0ae38218cb3301608231
