Fixes and enhancements of SIMD raidz parity

- Implementation lock replaced with atomic variable

- Trailing whitespace is removed from user specified parameter, to enhance
experience when using commands that add newline, e.g. `echo`

- raidz_test: remove dependency on `getrusage()` and RUSAGE_THREAD, Issue #4813

- silence `cppcheck` in vdev_raidz, partial solution of Issue #1392

- Minor fixes and cleanups

- Enable use of original parity methods in [fastest] configuration.
New opaque original ops structure, representing native methods, is added
to supported raidz methods. Original parity methods are executed if selected
implementation has NULL fn pointer.

Signed-off-by: Gvozden Neskovic <neskovic@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #4813
Issue #1392

include/sys/vdev_raidz_impl.h

@@ -89,13 +89,15 @@ typedef boolean_t	(*will_work_f)(void);
 typedef void		(*init_impl_f)(void);
 typedef void		(*fini_impl_f)(void);
 
+#define	RAIDZ_IMPL_NAME_MAX	(16)
+
 typedef struct raidz_impl_ops {
 	init_impl_f init;
 	fini_impl_f fini;
 	raidz_gen_f gen[RAIDZ_GEN_NUM];	/* Parity generate functions */
 	raidz_rec_f rec[RAIDZ_REC_NUM];	/* Data reconstruction functions */
 	will_work_f is_supported;	/* Support check function */
-	char *name;			/* Name of the implementation */
+	char name[RAIDZ_IMPL_NAME_MAX];	/* Name of the implementation */
 } raidz_impl_ops_t;
 
 typedef struct raidz_col {
@@ -127,6 +129,8 @@ typedef struct raidz_map {
 	raidz_col_t rm_col[1];		/* Flexible array of I/O columns */
 } raidz_map_t;
 
+#define	RAIDZ_ORIGINAL_IMPL	(INT_MAX)
+
 extern const raidz_impl_ops_t vdev_raidz_scalar_impl;
 #if defined(__x86_64) && defined(HAVE_SSE2)	/* only x86_64 for now */
 extern const raidz_impl_ops_t vdev_raidz_sse2_impl;