[sv-bc] re: text macros calls within string literals

This was discussed in Mantis 1119 (from ETF), but never resolved by
clarification of the text.

Shalom

> Let me summarize my understanding, including some things which
> you did
> not write explicitly.
> 
> Rule 1. If a string literal occurs within a text macro
> definition, then
> macro expansion does not occur inside it.