Improved expression logging.  Now all calls to
FindExternalVisibleDecls and FindExternalLexicalDecls
are marked and given unique IDs, so that all logging
done as part of their execution can be traced back to
the proper call.

Also there was some logging that really wasn't helpful
in most cases so I disabled it unless verbose logging
(log enable -v lldb expr) is enabled.

llvm-svn: 141987
diff --git a/lldb/source/Expression/ASTResultSynthesizer.cpp b/lldb/source/Expression/ASTResultSynthesizer.cpp
index db0714e..e78f09d 100644
--- a/lldb/source/Expression/ASTResultSynthesizer.cpp
+++ b/lldb/source/Expression/ASTResultSynthesizer.cpp
@@ -65,7 +65,7 @@
 
     if (NamedDecl *named_decl = dyn_cast<NamedDecl>(D))
     {
-        if (log)
+        if (log && log->GetVerbose())
         {
             if (named_decl->getIdentifier())
                 log->Printf("TransformTopLevelDecl(%s)", named_decl->getIdentifier()->getNameStart());