dxr-build: allow specifying tree build order

Add support for an optional |order| parameter tp tree configs; it should be
an integer, with smaller values being built first.  Trees with unspecified
order will be built after those with specified order, in sorted by tree
name.
Set LD_LIBRARY_PATH in the json-test makefile. This should solve bug 823322.

I'm not sure where that makefile comes from. If something generates it, we should fix this at the source.
Export compiler command lines in DXR-specific env variables.

Rather than just export CC and CXX environment variables, export the
same information as DXR-specific environment variables.  This helps
integration into non-GNU build systems.
Don't emit "type"s for declarations, only definitions.  Previously code
like:
	struct Foo;
	struct Foo;
	struct Foo {};
would emit one "type" and one "decldef" for each line.  This could
result in "Jump to Definition" going to the wrong place.  Now this code
results in one "decldef" for each of the first two lines and one "type"
for the last line.
Merge pull request #58 from abbeyj/testing

Don't emit "type"s for declarations, only definitions
Fix for failing tests due to not being able to locate libtrilite.so
Second attempt to fix "make test"
Make sure build is run before attempting to test.
Merge branch 'testing' of https://github.com/mozilla/dxr into testing
Add "const" to the end of the fully qualified name of const methods.
This avoids confusing two separate methods "void foo()" and
"void foo() const".
Fix libtrilite not getting built on test.

(Ripped off from abbeyj's pull req)
Merge abbeyj's LD_LIBRARY_PATH fixes in. I like his relative paths better.
Make the tests pass on Jenkins (once it has the Virtualbox kernel module loaded).
Tweak grammar in readme.

Really, I just want to see if Jenkins passes.
Add test files missing from previous commit.
Add a comment to the test harness.

This is all going to die soon, but at least I don't have to read the code again. :-)
Add a temporary script that `scp`s the checkout into the Vagrant VM on Jenkins so we can get CI passing.

Once https://bugzilla.mozilla.org/show_bug.cgi?id=826549 is done, we can remove this.
Make tests pass on Jenkins!

* Quit using NFS shared folders on Jenkins, since they don't work at the moment.
* Enable symlinks on the dxr shared folder so trilite will build.
* Make many tweaks to the Jenkins config:
  * Build our vagrant box manually rather than with the Jenkins plugin. Run the tests over ssh from a normal "execute shell" build step as well, since it doesn't find our manually-created box otherwise.
  * Get the path to vagrant executable right.
Stick the few lines of Jenkins shell script in a file so we can change-track it.
State what jenkins.sh does.