[PGO] Add simplified branch weights for Objective-C for-collection loops.

Conceptually one of these loops is just a while-loop, but the actual code-gen
is more complicated. We don't instrument all the different control flow edges
to get accurate counts for each conditional branch, nor do I think it makes
sense to do so. Instead, make the simplifying assumption that the loop behaves
like a while-loop. Use the same branch weights for the first check for an
empty collection as would be used for the back-edge of a while loop, and use
that same weighting for the innermost loop, ignoring the possibility that there
may be some extra code to go fetch more elements.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@204767 91177308-0d34-0410-b5e6-96231b3b80d8
Move the -i[no-]system-prefix options from CC1Options.td to Options.td.

Summary:
This allows them to be used without -cc1 the same way as -I and -isystem.
Renamed the options to --system-header-prefix=/--no-system-header-prefix to avoid interference with -isystem and make the intent of the option cleaner.

Reviewers: rsmith

Reviewed By: rsmith

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D3185

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@204775 91177308-0d34-0410-b5e6-96231b3b80d8
Add existing warnings to -Waddress so that it works closer to what GCC has.
Previously, -Waddress was empty.

Fixes PR9043.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@204776 91177308-0d34-0410-b5e6-96231b3b80d8