There's currently no API to determine the most recent version of node-webkit over the Web.

Note: `make clean` happens after `npm install nw-gyp -g` because we intend to use `nw-gyp` later to rebuild the existing build of node-sqlite3.

Release notes https://groups.google.com/d/msg/node-webkit/bPjur7aFaQc/4TP6o3SM-8sJ say that 0.8.4 fix improves the behaviour on OS X.

It seems (in installation logs) that nw-gyp does not contain any binary (i.e. compiled) addons.

Thus it's fine if nw-gyp survives 64bit→32bit switch of our Node.js environment on Linux.

This commit does also prepend `on Linux 64 bit:` to some comments (making it easier to understand what subplatform is targeted).

On Linux nw-gyp is installed earlier (in 64 bit mode) and thus we can refrain from its reinstallation for 32 bit, speeding things up.

Try a feature originally introduced in node-pre-gyp v0.4.2 commit mapbox/node-pre-gyp@370024a for mapbox/node-pre-gyp#14.

Working around a temporal inavailability of node-pre-gyp v0.4.2.

See mapbox/node-pre-gyp#35 for details.

Otherwise the following check fails:

https://github.com/springmeyer/node-pre-gyp/blob/3d4632a7333d420d6423299b143f5391b626e904/lib/util/versioning.js#L75-79

A pull request (mapbox/node-pre-gyp#36) is opened to land a partial fix for node-pre-gyp's validation process.

This commit uses a source branch of that pull request.

After this commit, node-pre-gyp's validator is expected to launch `nw` instead of `node-webkit` on Travis CI's Linux.

A former ENOENT error is expected to be replaced by a node-webkit's error when the engine realises it's given a node-sqlite3 module's JavaScript instead of some HTML5 application.

Commit Mithgol/node-pre-gyp@eaea6e1 is now included in the node-pre-gyp's source used here.

xvfb recipe:
http://docs.travis-ci.com/user/gui-and-headless-browsers/#Using-xvfb-to-Run-Tests-That-Require-GUI-(e.g.-a-Web-browser)

sleep 3 recipe:
http://docs.travis-ci.com/user/gui-and-headless-browsers/#Starting-a-Web-Server

More magic.

This commit also erases `sudo apt-get update --fix-missing` introduced in one of the previous commits, because it didn't help.

Follow the following suggestion:

http://askubuntu.com/questions/363878/how-to-install-32-bit-matlab-in-ubuntu-64-bit/363879#363879

As seen in http://www.maketecheasier.com/run-32-bit-apps-in-64-bit-linux/

Used “Search the contents of packages” at http://packages.ubuntu.com/

Found in “Search the contents of packages” at http://packages.ubuntu.com/ using “lucid” distribution (instead of default “saucy”).

This commit runs one `sudo apt-get -y install` for every package; otherwise each failure stops the whole installation process, but that makes the debugging painful (a test takes 13 minutes to run).

Two packages not found → removing.

The following `npm install` takes more than 3 seconds anyway; `xvfb` would already start before it becomes necessary for node-webkit.