Add new port math/opensolaris-libm

In 2006, Sun Microsystems released math and vector math libraries as
part of their effort to open-source Solaris:

libmvec - vector math library

This library contains function to evaluate common mathematical functions
for several arguments at once. The argument values are specified by one
or more vectors (arrays) of data, and the corresponding result values
are stored in another vector.

libm - C99 math library

Functions  in  this  library provide common elementary mathematical
functions and floating point environment routines defined by System V,
ANSI C, POSIX, and so on.  Additional functions in this library provide
extended support for handling floating point exceptions.

The original source has been modified to build on FreeBSD and DragonFly
using GCC or clang and the GNU assembler. All fixes introduced by Nexenta
and Illumos projects have also been incorporated. Missing x86_64 variants
of lrint and lround have added. The floating-point exception logging
including address->symbol tranlation has also been implemented.