[OG11][committed] OpenMP metadirective support

[Kwok Cheung Yeung]

Hello

I have backported and committed my metadirective patches onto the 
current OpenMP development branch (devel/omp/gcc-11). These are:

f464df13a44b9814341659be631f051377a2ce25 openmp: Add C support for 
parsing metadirectives
a238b6934b62ce3e8342047e41840c804d83b59d openmp: Add middle-end support 
for metadirectives
7e672d2ba146ca55dfffc36b198fbb3f3200f8f2 openmp: Add support for 
resolving metadirectives during parsing and Gimplification
b6fd3d1a54736c87fcd29a4ed294b31346b3af75 openmp: Add support for 
streaming metadirectives and resolving them after LTO
360db2054413d21399473173a85870da6479ab8c openmp: Add C++ support for 
parsing metadirectives
ceb0beb7ba9357146994895070762f8a9d94ca7c openmp, fortran: Add Fortran 
support for parsing metadirectives
eb4bea483010d91fbeeae9c863e92da873fbeef9 openmp: Add testcases for 
metadirectives
b597c0835ede0067d1b009e0d7381515b44d8753 openmp: Metadirective fixes
21766085775bd52c9db53629636c830fc9dc6fa0 openmp: Add support for 
'target_device' context selector set

The following backport from mainline was also required:

94c179971913b4837ec76a9e02a9a8a5cbf8e024 Expose stable sort algorithm to 
gcc_sort_r and add vec::stablesort

Thanks

Kwok