Better workaround for aliases of *_finite symbols in vector math library.

Old workaround based on assembly aliases can lead to link fail (bug 19058).
This patch makes workaround in another way to avoid it.

    [BZ #19058]
    * math/Makefile ($(inst_libdir)/libm.so): Added libmvec_nonshared.a
    to AS_NEEDED.
    * sysdeps/x86/fpu/bits/math-vector.h: Removed code with old workaround.
    * sysdeps/x86_64/fpu/Makefile (libmvec-support,
    libmvec-static-only-routines): Added new file.
    * sysdeps/x86_64/fpu/svml_finite_alias.S: New file.
    * NEWS: Mention this fix.