Ticket 168: Clarify behavior of polar and complex representations

From Malcolm Tredinnick:

If you mean the grammar specification in the <complex> production on page 13 of the R6RS report, then that's the same as in R7RS draft 1 and is similar all the way back to at least R4RS. However, the problem is that it's only describing a bunch of symbols, not semantics. That's not enough information for an implementer or for somebody wanting to verify correct behaviour. Nowhere is it mentioned that this *is* the polar form, for example, let alone whether the number after the "@" is interpreted as radians or degrees or even possibly pineapples. You cannot come to a recent Scheme report and get any understanding of what 1@2 actually means.