REGTESTS: converter: add url_dec test

while looking at `url_dec` implementation I realised there was not yet a
simple test to avoid future regressions.
This one is testing simple case, including the "+" behaviour depending
on the argument passed to `url_dec`

Signed-off-by: William Dauchy <wdauchy@gmail.com>
(cherry picked from commit a2a46ee5724ca10640caad2fd2cc8648e11c1d9c)
Signed-off-by: William Lallemand <wlallemand@haproxy.org>
1 file changed