Merging r155788:

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r155788 | rsmith | 2012-04-29 00:31:09 -0700 (Sun, 29 Apr 2012) | 4 lines

PR12688: ParseCXXClassMemberDeclaration's sometimes-null ThisDecl takes another
victim. Don't crash if we have a delay-parsed exception specification for a
class member which is invalid in a way which precludes building a FunctionDecl.

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llvm-svn: 156676