Bad deprecation warnings in numbers.c

[Neil Jerram]

There is a group of deprecation warnings in (stable) numbers.c that
say, for example:

  scm_c_issue_deprecation_warning ("`scm_mkbig' is deprecated. "
                                   "Use `scm_i_mkbig' instead.");

No!!!!!

This directly contradicts our aim of using `scm_i_' to mark Guile
internals, which libguile users shouldn't use _at all_!

What's the right thing here?  Could we do it before 1.6?

        Neil