Avoid a copy in RPC output

Split up HTTPReply into HTTPReply and HTTPReplyHeader, so that
the message data can be streamed directly.

Also removes a c_str(), which would have prevented binary
output with NUL characters in it.
Remove size limit in RPC client, keep it in server

The size limit makes a lot of sense for the server, as it never has to
accept very large data.

The client, however, can request arbitrary amounts of data with
`listtransactions` on a large wallet.

Fixes #4604.
build: Find the proper xcb/pcre dependencies
build: teach macdeploy the -translations-dir argument, for use with static qt

When QT is linked statically, macdeploy can't infer its paths. While plugins
and frameworks don't need to be packaged, translations still do (for now).
build: add --with-qt-translationdir to configure for use with static qt
build: hook up qt translations for static osx packaging
build: Fix 'make deploy' when binaries haven't been built yet
build: fix race in 'make deploy' for windows

The binary builds can clobber eachother, so use a single subdir dependency
instead.
Merge pull request #4640

733177e Remove size limit in RPC client, keep it in server (Wladimir J. van der Laan)
e17151a Avoid a copy in RPC output (Wladimir J. van der Laan)
Merge pull request #4645

6b271a3 build: fix race in 'make deploy' for windows (Cory Fields)
d343460 build: Fix 'make deploy' when binaries haven't been built yet (Cory Fields)
206a7f9 build: hook up qt translations for static osx packaging (Cory Fields)
d597219 build: add --with-qt-translationdir to configure for use with static qt (Cory Fields)
71941ce build: teach macdeploy the -translations-dir argument, for use with static qt (Cory Fields)
f8120f7 build: Find the proper xcb/pcre dependencies (Cory Fields)
eccd585 build: silence mingw fpic warning spew (Cory Fields)
a98356f build: don't let libtool insert rpath into binaries (Cory Fields)
travis: add WIP dependency builder.
travis: initial config
gitian: replace descriptors