CLI Buffer Sizes

[almann]

By default, the CLI tools (both ion and ionizer) have very small buffers for various things. A customer had a file, for example with a 90K byte string literal in it which causes the tool to fail with an undersized buffer error.

I patched the tools at commit https://github.com/amzn/ion-c/commit/353fdee98664c4581c37cf264fc001737bb63c28 to unblock the customer, however, we really should either take the above defaults and/or make this configurable.