[Bash-autocompletion] Pass all flags in shell command-line to Clang
Previously, we passed "#" to --autocomplete to indicate to enable cc1
flags. For example, when -cc1 or -Xclang was passed to bash, bash
executed clang --autocomplete=#-<flag they want to complete>.
However, this was not a good implementation because it depends -Xclang
and -cc1 parsing to shell. So I changed this to pass all flags shell
has, so that Clang can handle them internally.
I had to change many testcases because API spec changed quite a lot.
Reviewers: teemperor, v.g.vassilev
Differential Revision: https://reviews.llvm.org/D39342