CLEANUP: assorted typo fixes in the code and comments

This is 20th iteration of typo fixes
diff --git a/include/haproxy/atomic.h b/include/haproxy/atomic.h
index 709d4aa..cc06162 100644
--- a/include/haproxy/atomic.h
+++ b/include/haproxy/atomic.h
@@ -520,7 +520,7 @@
 	 * if we could apply the change. In order to pass a pair, we simply map
 	 * a register pair on a struct so that the compiler can emit register
 	 * pairs that we can use thanks to the undocumented "%H" modifier
-	 * mentionned on the link below:
+	 * mentioned on the link below:
 	 *   https://patchwork.ozlabs.org/project/gcc/patch/59368A74.2060908@foss.arm.com/
 	 */
 	struct pair { uint64_t r[2]; };