Manage MERGE statement like CASE statement. Bug #3499664.
Manage MERGE statement like CASE statement.
Bug #3499664.

R1dO/scintilla_clone,R1dO/scintilla_clone,R1dO/scintilla_clone,R1dO/scintilla_clone,R1dO/scintilla_clone,R1dO/scintilla_clone,R1dO/scintilla_clone,R1dO/scintilla_clone