Make sure that ClangExpressionDeclMap doesn't
live beyont parsing.  This is important because
all the ClangASTImporter::Minions for a parser's
ASTContext are cleared when ClangExpressionDeclMap
is deleted.

This resolves many hard-to-reproduce crashes,
especially ones involving breakpoint conditions.

<rdar://problem/14775391>


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@189080 91177308-0d34-0410-b5e6-96231b3b80d8