Add range accessors for captures of a LambdaExpr.

Summary:
This adds LambdaExpr::captures(), LambdaExpr::explicit_captures()
and LambdaExpr::implicit_captures() as simple wrappers over the underlying
*_begin()/*_end() functions.

Reviewers: aaron.ballman

Differential Revision: http://reviews.llvm.org/D3926

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@209679 91177308-0d34-0410-b5e6-96231b3b80d8
Add a test that we don't store stale modtime in modules

The change from r209195 turned out to be important to avoid saving stale
modification time/expected size information in a module file when there
are 3 or more modules in a dependency chain and the bottom one is
rebuilt. So add a test for that.

rdar://problem/17038180

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@209682 91177308-0d34-0410-b5e6-96231b3b80d8
Retain isImplicit flag for local variable declarations when instantiating
templates.

Reviewers: rsmith

Reviewed By: rsmith

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D3924

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@209686 91177308-0d34-0410-b5e6-96231b3b80d8