Document procedures in `(scheme list)` / SRFI 1

Hi @egallesio !

This is just an idea. We could bring documentation for SRFI procedures and macros so the user can have online help. However, I suppose there should be compile options to generate (or not) documentation:

for SRFIs
for STklos libraries
for standard Scheme libraries So far I just included the documentation in SRFI 1. And I believe I had already done for SRFI 25.

This PR also removes the implementation of last-pair, which is already in STklos core. I also reordered some of the procedures when writing the documentation.

egallesio / STklos

Document procedures in `(scheme list)` / SRFI 1 #637