ARM: Implement sqrt in inline assembly.

Call VSQRT directly to avoid the tiniest (1ulp) precision
error that occurs in the system-supplied sqrt on QNX/ARM.

All precision tests in SunSpider are now passing on this platform.

BUG=
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/98363010

Patch from Cosmin Truta <ctruta@gmail.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18506 ce2b1a6d-e550-0410-aec6-3dcde31c8c00