* module/web/uri.scm (declare-default-port!): New function, declares a
default port for a scheme. Predeclare default ports for http and
https.
(unparse-uri): If the port is the default port for the given scheme,
don't serialize the port part of the URI.
* module/web/toy-server.scm (serve-client): Fix up error handling, so we
catch errors when reading, handling, and writing. If we run
interactively, an error will enter the debugger.
* module/web/http.scm: New module, declares known HTTP headers, and
their parsers and unparsers.
* test-suite/tests/web-http.test: Add test suite.
* module/Makefile.am:
* test-suite/Makefile.am: Adapt.
* module/web/uri.scm (uri-error): New proc, throws to 'uri-error.
(validate-uri, uri-decode, uri-encode): Use uri-error.
* test-suite/tests/web-uri.test: Update for uri-error.
