Remove unnecessary casts.
Pre-allocate memory in readAll() if possible and remove the 0 special case for max_bytes.

Note that max_bytes==0, for backwards compatibility, still will accept any number of bytes, but will result in an  error later at some point.
Improve error message output in default main().
Fix GCAllocator.realloc to handle changed alignment of the realloc'ed block correctly.

It seems like GC.realloc also sometimes didn't copy the whole content of the original block.

This bug has at least caused data corruption for chunked HTTP responses.
Validate Allocator.realloc results in AllocAppender.
Improve diagnostics and error handling in Chunked(In/Out)putStream.
Reimplement Zlib(In/Out)putStream using etc.c.zlib directly instead of std.zlib.

The std.zlib API makes it necessary to allocate GC memory for every chunk of data written to zlib. Using zlib directly still requires external input/output buffers, but those can be reused now.
LibeventTCPConnection.write blocks now. Fixes #191.