Adding GNUABI aliases to non-GNUABI functions

[shibatch]

I am planning to add aliases that conform to the GNU Vector ABI specification to the functions whose names start with Sleef_. By doing this, compilers including GCC and Clang will be able to utilize SLEEF functions with their automatic vectorizers. For example,

The Intel version of Sleef_sind2_u10 will have an alias _ZGVbN2v_Sleef_sin_u10. The Intel version of Sleef_sind4_u10 will have an alias _ZGVcN4v_Sleef_sin_u10.

If a weak alias is not supported by the compiler that compiles SLEEF library, functions with the corresponding names are added instead.

This change will not affect the current GNUABI version of functions.

[fpetrogalli]

This sounds good to me.