libc: fix __cxa_atexit implicit declaration

Change-Id: Iacad18b332a717e4485c83df4bd42a850ff7699f
[ARM] libm: reimplement reimplementation of a few fp functions

combination of vanir's sin/cos/sqrt/sqrtf optimizations for krait/etc. + 2 commits by synergydev:

https://github.com/codefireXperiment/bionic/commit/5b1ece28ccc897c302c83b85bf86e2d736db72e6
https://github.com/codefireXperiment/bionic/commit/a1fcb3341f592f57e9ac845e1be92de23e3a9820

Change-Id: I879a2cefa2fa4415895f3afb7a3182c9af090495
Fix e_pow issue on non-krait stuff

Change-Id: I82675ee4c9762d141c2ff005d56de1a28ce5cea6
Revert all of those tweaks because something in them broke LPA playback on S4

Change-Id: Ib1f601620e7d66310c6389f5f3055ed58bea8b0b