fix malformed variable reference in makefile
implement StringWriter.getBuffer

This is used by json.org's JSON library.
use .dylib instead of .jnilib as OS X library suffix

This matches the behavior of System.mapLibraryName on
JDK 7 and later.
Merge pull request #362 from dicej/master

StringWriter.getBuffer, System.mapLibraryName, and makefile cleanup