runtime(bitbake): fix multiline Python function parameter syntax

runtime(bitbake): fix multiline Python function parameter syntax

Fix syntax highlighting for def-style Python functions, with their
parameters spanning multiple lines. E.g. the following should match as
valid Python code in Bitbake recipes:

    def myFunction(one, two, \
                   three, four):
        pass

For this to work, use the prefix modifier "\_" before the wildcard ".",
to also match newline characters.

closes: #18565

Signed-off-by: Martin Schwan <m.schwan@phytec.de>
Signed-off-by: Christian Brabandt <cb@256bit.org>