src/pmc/integer.c: Implement Complex and BigInt RHS values for the pow() functions

[jkeenan]

This ticket tracks an item previously tracked in the RT system at  RT #46631.

The following TODO item is found in src/pmc/integer.c:

1007 =item C<void i_pow_int(INTVAL value)>
1008 
1009 Raises SELF to the C<value>th power.
1010 
1011 TODO:  RT #46631 Complex and BigInt rhs.
1012 
1013 =cut

In the original RT, Paul Cochrane commented: This applies to all pow()-related functions, and means that the case when the right-hand-side value is complex or a BigInt needs to be implemented.