Fix gcc c90 compliance warnings

Fix non-c90 compliant code, for the most part these changes
simply deal with where a particular variable is declared.
Under c90 it must alway be done at the very start of a block.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

lib/libuutil/uu_misc.c

@@ -209,7 +209,11 @@ uu_panic(const char *format, ...)
 int
 assfail(const char *astring, const char *file, int line)
 {
+#if defined(__STDC__) && __STDC_VERSION__ - 0 >= 199901L
+	__assert_c99(astring, file, line, "unknown func");
+#else
 	__assert(astring, file, line);
+#endif
 	/*NOTREACHED*/
 	return (0);
 }

lib/libzfs/libzfs_import.c

@@ -410,7 +410,9 @@ refresh_config(libzfs_handle_t *hdl, nvlist_t *config)
 boolean_t
 vdev_is_hole(uint64_t *hole_array, uint_t holes, uint_t id)
 {
-	for (int c = 0; c < holes; c++) {
+	int c;
+
+	for (c = 0; c < holes; c++) {
 
 		/* Top-level is a hole */
 		if (hole_array[c] == id)