gst/gststructure.c: When deserialising foo=bar without a type cast, check if it's...

gst/gststructure.c: When deserialising foo=bar without a type cast, check if it's a boolean before falling back to a ...

Original commit message from CVS:
* gst/gststructure.c: (gst_structure_parse_value):
When deserialising foo=bar without a type cast, check if it's a
boolean before falling back to a string type, otherwise things like
audiotestsrc ! audio/x-raw-int,signed=true ! fakesink won't work,
because the filtercaps end up having a signed=(string)true field,
which causes problems later when intersection caps.
* tests/check/gst/gststructure.c: (GST_START_TEST):
Add a unit test for this.