This yields a 20% improvement on the "read-string" benchmark.
* module/ice-9/rdelim.scm (read-string): Rewrite as a 'case-lambda',
with a tight loop around 'read-char', and without using
'read-string!'.
* test-suite/tests/rdelim.test ("read-string")["longer than 100 chars,
with limit"]: New test.
* benchmark-suite/benchmarks/ports.bm ("rdelim")["read-string"]: New
benchmark.
Moved ice-9/ and oop/ under module/, with the idea being that we have
only scheme under module/. Adjusted configure.in and Makefile.am
appropriately. Put oop/ at the end of the compilation order.
