THRIFT-929. cpp: Remove TZlibTest dependency on filesystem data

THRIFT-929. cpp: Remove TZlibTest dependency on filesystem data

Previously, ZlibTest read a file from disk to get data to test with.
It would fail unless gen-cpp/DebugProtoTest_types.tcc was present in the
current directory and was at least 32kB long.

Now ZlibTest simply generates 3 separate buffers to test with.  The
first buffer is just all "a"s, the second is some random sequential
runs, and the third is completely random.  They usually seem to have
compression ratios of around 315:1, 4:1, and 1:1, respectively.

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@1005148 13f79535-47bb-0310-9956-ffa450edef68