libgpiod

Use double '/' for escaping regex special characters for patterns in
python strings to silence the following warnings:

bindings/python/tests/tests_edge_event.py:211: SyntaxWarning: invalid escape sequence '\.'
  "<EdgeEvent type=Type\.RISING_EDGE timestamp_ns=[0-9]+ line_offset=0 global_seqno=1 line_seqno=1>",
bindings/python/tests/tests_info_event.py:188: SyntaxWarning: invalid escape sequence '\.'
  '<InfoEvent type=Type\.LINE_REQUESTED timestamp_ns=[0-9]+ line_info=<LineInfo offset=0 name="None" used=True consumer="\?" direction=Direction\.INPUT active_low=False bias=Bias\.UNKNOWN drive=Drive\.PUSH_PULL edge_detection=Edge\.NONE event_clock=Clock\.MONOTONIC debounced=False debounce_period=0:00:00>>',

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>