Merge branch 'bld/clang' into next

* bld/clang:
  Summary: chore, kick ase extern inline Keywords: code hygiene build clang
  Summary: chore, don't check for extern inline support anymore Keywords: code hygiene build clang
  Summary: chore, crunch the number of extern_inline definitions Keywords: code hygiene build clang
  Summary: chore, refactor nested function construct in event-Xt.c Keywords: build clang
  Summary: chore, replace nested function construct by cpp equivalent Keywords: build clang