Refine SourceManager's isBeforeInTranslationUnit() cache to have more entries.

isBeforeInTranslationUnit() uses a cache to reduce the expensive work
to compute a common ancestor for two FileIDs.  This work is very
expensive, so even caching the latest used FileIDs was a big win.
A closer analysis of the cache before, however, shows that the cache
access pattern would oscillate between a working set of FileIDs, and
thus caching more pairs would be profitable.

This patch adds a side table for extending caching.  This side table
is bounded in size (experimentally determined in this case from
a simple Objective-C project), and when the table gets too large
we fall back to the single entry caching before as before.

On Sketch (a small example Objective-C project), this optimization
reduces -fsyntax-only time on SKTGraphicView.m by 5%.  This is
for a project that is already using PCH.

Fixes <rdar://problem/13299847>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@176142 91177308-0d34-0410-b5e6-96231b3b80d8
[analyzer] If a struct has a partial lazy binding, its fields aren't Undef.

This is essentially the same problem as r174031: a lazy binding for the first
field of a struct may stomp on an existing default binding for the
entire struct. Because of the way RegionStore is set up, we can't help
but lose the top-level binding, but then we need to make sure that accessing
one of the other fields doesn't come back as Undefined.

In this case, RegionStore is now correctly detecting that the lazy binding
we have isn't the right type, but then failing to follow through on the
implications of that: we don't know anything about the other fields in the
aggregate. This fix adds a test when searching for other kinds of default
values to see if there's a lazy binding we rejected, and if so returns
a symbolic value instead of Undefined.

The long-term fix for this is probably a new Store model; see
<rdar://problem/12701038>.

Fixes <rdar://problem/13292559>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@176144 91177308-0d34-0410-b5e6-96231b3b80d8
Reapply r176133 with testcase fixes.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@176145 91177308-0d34-0410-b5e6-96231b3b80d8
Don't crash when diagnosing path-constrained protected
access to a private member to which we have special access.

rdar://12926092

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@176146 91177308-0d34-0410-b5e6-96231b3b80d8
comment parsing: Properties are considered like methods, and people 
think of them as having return values that may be computed. Don't
warn when using @return in their comment. // rdar://13189938


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@176147 91177308-0d34-0410-b5e6-96231b3b80d8