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/internals/body-parsing.txt b/doc/internals/body-parsing.txt
index 45d7034..be209af 100644
--- a/doc/internals/body-parsing.txt
+++ b/doc/internals/body-parsing.txt
@@ -81,7 +81,7 @@
 
 msg.sol  : start of line. Points to the beginning of the current header line
            while parsing headers. It is cleared to zero in the BODY state,
-           and contains exactly the number of bytes comprising the preceeding
+           and contains exactly the number of bytes comprising the preceding
            chunk size in the DATA state (which can be zero), so that the sum of
            msg.sov + msg.sol always points to the beginning of data for all
            states starting with DATA. For chunked encoded messages, this sum
@@ -91,7 +91,7 @@
            TRAILERS state, it contains the length of the last parsed part of
            the trailer headers.
 
-msg.eoh  : end of headers. Points to the CRLF (or LF) preceeding the body and
+msg.eoh  : end of headers. Points to the CRLF (or LF) preceding the body and
            marking the end of headers. It is where new headers are appended.
            This offset is automatically adjusted when inserting/removing some
            headers. It always contains the size of the headers excluding the