patch 9.0.0828: various typos

Problem:    Various typos.
Solution:   Correct typos. (closes #11432)
diff --git a/src/regexp.c b/src/regexp.c
index b15dc3a..e29e6ea 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -1890,7 +1890,7 @@
  * vim_regexec_multi() match.
  *
  * If "flags" has REGSUB_COPY really copy into "dest[destlen]".
- * Oterwise nothing is copied, only compue the length of the result.
+ * Otherwise nothing is copied, only compute the length of the result.
  *
  * If "flags" has REGSUB_MAGIC then behave like 'magic' is set.
  *