Originally DiSL classes could not contain other than annotated
snippet methods. This relaxes the SnippetParser to allow other
methods to be present in DiSL class and it also only warns on
snippets with multiple annotations (instead of throwing an
exception).

This allows to combine guard classes and static methods used
from guard classes with the snippet code. This makes small-scale
instrumentation more self-contained. We should make sure that
snippet code does not try to invoke those methods though.