[Users] glib regex issue is stopping OAuth2 token update

[Dan N]

I've been successfully using OAuth2 (In Production, claws-mail 4.1.0, Linux)
with gmail POP for a few months, ever since gmail began requiring it.  Starting
3-4 weeks ago something changed in Google's server response causing random
failures (at least once a day) of token update and giving log message "OAuth2
access token not obtained".  Retrying "Get Mail" usually succeeds in getting an
updated token but sometimes it takes 3-4 tries before it works.

I tracked the problem down to the glib function g_regex_match failing whenever
the google server returns non-ascii characters in its response ("\247" in the
case I debugged, but I've seen other values), even though that character is
near the end and nowhere close to the strings being matched.  I confirmed this
with a test program and also confirmed a workaround.

I have no idea what the ideal fix is, but my workaround is to use G_REGEX_RAW
on all 3 of the g_regex_new calls in oauth2.c:

-       regex = g_regex_new ("\"access_token\": ?\"(.*?)\",?", 0, 0, NULL);
+       regex = g_regex_new ("\"access_token\": ?\"(.*?)\",?", G_REGEX_RAW, 0, NULL);

-       regex = g_regex_new ("\"expires_in\": ?([0-9]*),?", 0, 0, NULL);
+       regex = g_regex_new ("\"expires_in\": ?([0-9]*),?", G_REGEX_RAW, 0, NULL);

-       regex = g_regex_new ("\"refresh_token\": ?\"(.*?)\",?", 0, 0, NULL);
+       regex = g_regex_new ("\"refresh_token\": ?\"(.*?)\",?", G_REGEX_RAW, 0, NULL);