This patch adds infrastructure for addition of SIMD

This patch adds infrastructure for addition of SIMD
declarations for math functions in math.h. Added new headers math-vector.h
(only generic version for now) and libm-simd-decl-stubs.h with empty
definitions required for proper unfolding of new macros __MATHCALL_VEC which
will be used for declaration of vector math functions.

2015-05-14  Andrew Senkevich  <andrew.senkevich@intel.com>

    * bits/math-vector.h: New file.
    * bits/libm-simd-decl-stubs.h: New header.
    * math/Makefile (headers): Added new header libm-simd-decl-stubs.h.
    * math/math.h (__MATHCALL_VEC): New macro.