Merge branch 'releases/gcc-11' into devel/omp/gcc-11

Merge up to 271fc1caac433e84e6389e73a5bf07350ea545e2 (May 20, 2021)

diff --cc gcc/cp/cp-tree.h
Simple merge

diff --cc gcc/cp/pt.c
Simple merge

diff --cc gcc/doc/invoke.texi
Simple merge