[R6RS] Adopting SRFI 1 procedures

[Anton van Straaten]

This would be the minimal set of procedures I would pick to adopt from 
SRFI-1:

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Of course, there are many other worthy candidates for adoption, but 
these procedures are the ones which I find are most often required by 
themselves.  If they were standard procedures, it would eliminate the 
need to load SRFI 1 in many cases.

Anton