Fixed style issues with variable ordering and naming, spacing and

Fixed style issues with variable ordering and naming, spacing and
parentheses.

Fixed alignment issue in gr_dup() in its assignment of gr_mem using a
struct to force alignment without performing alignment mathematics.  This
was noticed recently with libutil was built with WARNS=6 on platform such
as sparc64.

Added checks to gr_dup(), gr_equal() and gr_make() to prevent segfaults
when examining struct group's with the struct members pointing to NULL's.

With fix of alignment issue, restore WARNS?=6.

Reviewed by:	des
MFC after:	1 week