* src/vipw.c: Document the sections closed by #endif

	* src/vipw.c: Document the sections closed by #endif
	* src/vipw.c: Avoid implicit conversion of pointers or integers to
	booleans.
	* src/vipw.c: Added brackets and parenthesis.
	* src/vipw.c: Limit the definition of some variables and macros to
	the WITH_TCB scope.
	* src/vipw.c: Avoid assignment in comparisons.
	* src/vipw.c: Replace PASSWD_FILE (resp. GROUP_FILE and
	SGROUP_FILE) by pw_dbname () (resp. gr_dbname () and sgr_dbname ()).
	This is more consistent with the shadow file handling and may be
	useful to allow edition of another partition's files.