pgrep gives a warning if the match string is longer than
15 characters and there was no match. That often does not
make sense when using regex or at the very least difficult
to know when to warn users. e.g
"1234567890|123456789X" is a 21 character string but only
matching two 10 string words.

pgrep has a simple check for regex and will now suppress
that warning if that has been used.

References:
 https://bugs.debian.org/1037450



Signed-off-by: Craig Small <csmall@dropbear.xyz>