While all systems that I have access to support strcasestr, it is
in fact not part of POSIX. So here's a fallback reimplementation
based on POSIX functions.
Signed-off-by: Dirk Hohndel <hohndel@infradead.org>
Tested-by: Tomas Carnecky <tom@dbservice.com> (on OpenSolaris snv_134)
