Run iconv -f latin1 -t utf-8 on lhttpc files.

Otherwise build on Erlang/OTP 17 fails because of the following
warning:

Non-UTF-8 character(s) detected, but no encoding declared. Encode the file in UTF-8 or add "%% coding: latin-1" at the beginning of the file. Retrying with latin-1 encoding.

Change-Id: Iae6ed537f4e29984a48ec50494a8655330e764ec
Reviewed-on: http://review.couchbase.org/35584
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>
Tested-by: Filipe David Borba Manana <fdmanana@gmail.com>