DOC: Fix typos in different subsections of the documentation

Fix typos found in the design-thoughts, internals and lua-api
subsections of the documentation.
diff --git a/doc/design-thoughts/connection-reuse.txt b/doc/design-thoughts/connection-reuse.txt
index 2b92836..4eb22f6 100644
--- a/doc/design-thoughts/connection-reuse.txt
+++ b/doc/design-thoughts/connection-reuse.txt
@@ -202,7 +202,7 @@
 |       least with some transport not de-initialized. We might thus need
 |       conn_xprt_close() when conn_xprt_init() fails.
 | 
-| The fd should be conditionned by ->ctrl only, and the transport layer by ->xprt.
+| The fd should be conditioned by ->ctrl only, and the transport layer by ->xprt.
 | 
 | - conn_prepare_ctrl(conn, ctrl) 
 | - conn_prepare_xprt(conn, xprt)