DOC: clarify matching strings on binary fetches

Add clarification and example to string matching on binary samples,
as comparison stops at first null byte due to strncmp behaviour.

Backporting all the way down to 1.5 is suggested as it might save
from headaches.

(cherry picked from commit cb250fc9843a335fffe44ed6b15570e5b7cd2a35)
Signed-off-by: Willy Tarreau <w@1wt.eu>
(cherry picked from commit 31f3f5e5fecc6dcec08497b06df8267aad62e0ae)
Signed-off-by: Willy Tarreau <w@1wt.eu>
1 file changed