BUG/MINOR: tools: Reject size format not starting by a digit

BUG/MINOR: tools: Reject size format not starting by a digit

parse_size_err() function is now more strict on the size format. The first
character must be a digit. Otherwise an error is returned. Thus "size k" is
now rejected.

This patch must be backported to all stable versions.

(cherry picked from commit 82635a0fc1d8196e5b199e2948d2bea4b1217ace)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 7f955e66b93625ad405405f10bd51b94ffff72fe)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 9a1194430a7d3a967c75775a801e99303b85dbc3)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>