Make srfi/*.scm main implementation files

[shirok]

Currently, many srfis are implemented in srfi-.scm, and we have an alias in srfi/.scm which are auto-generated from srfis.scm.

It is advantageous to make srfi/.scm implementation and srfi-.scm alias, however.

• R7RS code imports (srfi n), so it's more consistent that Gauche code imports srfi.n.
• When we implement draft srfi, we may have test code that imports (srfi n). However, currently the srfi/n.scm alias is only made if we have the entry in srfis.scm, but the entry only added when the srfi is officially supported.

[pclouds]

It is advantageous to make srfi/.scm implementation and srfi-.scm alias

Out of curiosity, what are the advantages?

[shirok]

As I itemized below that line. The more important one is the second factor; before srfi becomes finalized, I don't want to add its entry to src/srfis.scm, because adding entry to it means it's officially supported. If it isn't in src/srfis.scm, however, srfi/N.scm isn't created automatically. On the other hand, the tests from the reference implementation refers it with (srfi n), so we need srfi/N.scm to run the test.