Mat 403. Add off heap memory manager.

**This PR:**
* Adds the off heap aligned memory manager to OG-Maths.
* Adds windows port of the above (no `posix_memalign()` on windows).
* Is a stub more more general off heap memory operations.
* Gets ticket [[MAT-414]](http://jira.opengamma.com/browse/MAT-414) for addition work to gracefully handle exits. Rather suspect an API change will be required so a "status" can propagate to a C++ handler which then throws exceptions back to java.

**Coverage** (bearing in mind we are covering OS level stuff):
Java: 76% (up 3%, new code covered to 99%)
build/src/jshim 0.8% (no change)
build/src/librdag 16.4% (no change)
src/jshim 53.7% (down 1.3% mainly due to new JNI pass through functions for memory manipulation)
src/librdag 91.0% (down 0.3%, largely due to debug statements in `mem.cc`)
src/librdag/runners 95.7% (no change)