Inaccurate deprication warning in scm_dbl2big

[Mike Gran]

In Guile 1.6.4, numbers.c, in the definition of scm_dbl2big(), the 
function issues a deprecation warning, advising the programmer to use 
'scm_dbl2num' instead.

'scm_dbl2num' doesn't exist.  Should it actually be 'scm_double2num'?

This doesn't seem to be a problem with the CVS version of numbers.c, 
since the function definition, and thus the warning, don't appear in 
numbers.c.