build.xml: removed unzip-arm-toolchain
build.xml: renamed unzip-tool to untar-tool
build.xml: made untar-tool (and dependencies) easier to reuse
build.xml: removed unzip-avr-toolchain and unzip-libastyle in favour of unzip
build.xml: moved checksum into untar-unzip-checksum
build.xml: tar autodetects archive type, removing "z" flag
Merge pull request #2348 from arduino/ide-1.5.x-build-xml-refactor

ant build.xml refactor