Allow memory-mapped buffers to be forcibly unmapped.

This can be useful in memory-constrained environments (Android Studio running
out of address space in a 32-bit JVM). For Windows in particular, it allows
recently-unmapped files to be deleted, otherwise delete()/deleteOnExit() have
no effect.

Change-Id: Iedf04c6702d011c9cf575cb472eb85919b776b4c
2 files changed