Added radix command to set a default radix for resuts

This patch allows the user to see a different base (hex, octal, binary) by default.  The patch does not attempt to convert bases, but simply apply the default radix to results of commands.  This is most effective in interactive mode, as you can see values of a different base without having to resort to the format command.

Example:
. radix 2
. expr 10 + 2
0b1100
. expr 5 + 1
0b110
. puts 10
10 <--- does not try to convert bases on already existing numbers :)