Adding JavaScript syntax support for JavaScriptBuild (.jsb) files

jsb is a meta build system [1] which can generate actual build files for GNU make, ninja, visual studio etc.

These files are pure javascript files. Just to differentiate them from rest of the javascript files, these are marked as .jsb file.

[1] https://github.com/vivekgalatage/jsb
Sample JSBuild file showing the usage javascript as scripting language.
Merge pull request #1546 from vivekgalatage/master

Adding JavaScript syntax support for JavaScriptBuild (.jsb) files