AST dumping: dump template instantiations only once

Fixes infinite loop in PR15220.

Patch by Philip Craig.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175805 91177308-0d34-0410-b5e6-96231b3b80d8
Remove superfluous null pointer check.  The pointer is used prior to this check.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175807 91177308-0d34-0410-b5e6-96231b3b80d8
Replace ProgramPoint llvm::cast support to be well-defined.

See r175462 for another example/more details.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175812 91177308-0d34-0410-b5e6-96231b3b80d8
Remove the SplitDebug action and replace with a set of commands
in the compilation setup. Note that this doesn't currently
work for -no-integrated-as.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175813 91177308-0d34-0410-b5e6-96231b3b80d8
Don't pass -split-dwarf= to the backend unless we're on linux for
now.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175814 91177308-0d34-0410-b5e6-96231b3b80d8
Fix formatting and tabs in file.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175815 91177308-0d34-0410-b5e6-96231b3b80d8
Add back implicitly dropped const.

(found due to incoming improvements to llvm::cast machinery that will error on
this sort of mistake)

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175817 91177308-0d34-0410-b5e6-96231b3b80d8