ffmpeg: add caveats to document AAC encoder switch
llvm: use absolute dylib IDs

Fixes #32566.
llvm: build libcxx when building clang

Fixes #31754.
llvm: bump revision
llvm: update 3.5.0_1 bottle.
llvm: drop manual installation of cmake modules

cmake modules are installed by default since
https://github.com/llvm-mirror/llvm/commit/4c56efbd441d17b61f3e29ee2372e6e460d5a185

Closes #29976.
llvm: enable RTTI when building libc++
llvm: install scan-view and scan-build

Closes #33777.
llvm: install clang-tools-extra

Closes #35192.
llvm: bump revision
llvm: update 3.5.0_2 bottle.