Adds convenience uncompress and inflate procs to zlib.

The new uncompress() version doesn't require you to know the size of the
inflated destination buffer. The inflate() proc wraps it for convenience
on a var string type.
Modifies inflate() to return a discardable bool. Refs #1048.
Uses swap() to avoid variable copies. Refs #1048.
Uses finally as statement to release zlib memory. Refs #1048.
Merge pull request #1048 from gradha/pr_adds_convenience_uncompress_to_zlib

Adds convenience uncompress and inflate procs to zlib.