lang/gcc11: New port cloned from gcc11-devel

Welcome GCC 11.1, the first release of the GCC 11 series!

https://gcc.gnu.org/gcc-11/changes.html has a comprehensive overview
of many improvements and changes and
https://gcc.gnu.org/gcc-11/porting_to.html highlights issues you may
encounter porting to this version. This release series should not
prove too disruptive, mainly C++ defaulting to GNU++17 and some more
libstdc++ headers will need to be included explicitly.

To give a brief overview of some of the more noticable changes:

Some short options of the gcov tool have been renamed: -i to -j and
-j to -H.

Debugging information defaults to DWARF 5.

Vectorizer improvements, a new IPA-modref pass to track side effects
of function calls and improve precision of points-to-analysis, better
interprocedural constant propagation (IP-CP), smaller link-time
optimization (LTO) object files.

OpenMP 4.5 is now fully supported and OpenMP 5.0 support has been
extended.

A set of new warnings including -Wmismatched-dealloc, -Wsizeof-array-div,
-Wstringop-overread, and enhancements to existing warnings.

Several new features from the upcoming C2X revision of the ISO C
standard are supported with -std=c2x and -std=gnu2x.

Several C++20 features have been implemented and even some of the
upcoming C++23 draft features with the -std=c++23 and the like.

libstdc++ features improved C++17 support.

And, last but not least, loads of improvements for all of FreeBSD's
architectures.