remove invalid workaround for expf (glibc), 2X speedup

there was a workaround for x86_64 for glibc bug (4years ago),
where expf was slower than exp, so exp was used as a workaround.

that is not true anymore, use expf()  and code is 2X faster.

See and test: https://bugzilla.redhat.com/show_bug.cgi?id=521190
add NTA_ASM flag to optimizations, wrap all assembly code with it

define a new optimization flag NTA_ASM that enables our hand written ASM code be used.
It's important for debug/porting, where the ASM might not be able to run
check for SSE suppurt on all platforms

using PIC compilant ASM
10X speedup for MacOS, use vDSL functions

use SSE instructions with vDSL/vecLib in some cases.
Was enabled for darwin86 only, now add darwin64 too.
avoid code duplication, use checkSSE for other file

int checkSSE is defined in nta/math/array_algo.hpp
use it in bool checkSSE from nta/algorithm/svm.hpp to aviod
code duplication.