#12 Patch to make the reader optionally case sensitive

[Thomas Munro]

Hi,
We found when moving Scheme from another implementation to TinyScheme that we needed to use case sensitive symbols. Many implementations are case sensitive when reading symbols, since R6RS and R7RS changed from case insensitive to case sensitive, and many other implementations allow you to switch the reader's case sensitivity at runtime. This patch makes TinyScheme's reader configurable at runtime by calling (read-case-sensitive #t/#f). Please consider accepting this patch into TinyScheme.
Many thanks,
Thomas Munro