CLEANUP: assorted typo fixes in the code and comments

This is 8th iteration of typo fixes
diff --git a/include/types/fd.h b/include/types/fd.h
index b4535af..178dea1 100644
--- a/include/types/fd.h
+++ b/include/types/fd.h
@@ -118,7 +118,7 @@
 
 /* info about one given fd */
 struct fdtab {
-	unsigned long running_mask;          /* mask of thread IDs currntly using the fd */
+	unsigned long running_mask;          /* mask of thread IDs currently using the fd */
 	unsigned long thread_mask;           /* mask of thread IDs authorized to process the fd */
 	unsigned long update_mask;           /* mask of thread IDs having an update for fd */
 	struct fdlist_entry update;          /* Entry in the global update list */