Bug #984: Addition of a semantic patch file for showing unnecessary checks before a few known functions

This semantic patch pattern tries to find source code places where a check
is performed for an expression that is passed to a function (like "free")
which checks this single parameter itself for usability.
Redundant value or pointer checks can be avoided here.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Add a 1cocci target to be used like this: make 1cocci COCCITEST=nameofthetest
sbuf_delete does not check null first
Remove useless comparison to NULL before freeing variables