gdb: improve debug output of function overload resolution

gdb: improve debug output of function overload resolution

Function overload resolution prints debug output if turned on via the
'set debug overload' command.  The output includes the badness vector
(BV).  For each function, this vector contains a badness value of the
length of parameters as its first element.  So, BV[0] does not
correspond to a parameter.  The badness values of parameters start
with BV[1].

A badness value is a pair; it contains a rank and a subrank.  Printing
both fields provides useful information.

Improve printing the badness vector along these lines.

gdb/ChangeLog:
2019-11-29  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>

	* valops.c (find_oload_champ): Improve debug output.

Change-Id: I771017e7afbbaf4809e2238a9b23274f55c61f55