Scan the source for POSIX includes outside of the
allowed locations in check_format.sh. This only
tests for POSIX headers - not Linux Standards Base.
Also, fix one bug that was caught by this addition.
Change-Id: Ib0ca93fe6ac552dc49d95b27b4803e40282027e8
Signed-off-by: Ben Walker <benjamin.walker@intel.com>