Log message:
As proposed in following mail:
  http://mail-index.netbsd.org/pkgsrc-users/2013/11/16/msg018897.html

(1) Import nios2-binutils 2.23 (CodeSourcery derived) from wip.
(2) nios2-gcc41 now does not include nios2/Makefile.common,
    and unnecessary buildlink3 line to kpathsea removed.
(3) Switch nios2/Makefile.common to provide above (1) package.
(4) Import nios2-gcc 4.7.3 (CodeSourcery derived) from wip,
   including file (3) nios2/Makefile.common and DEPENDS (1) binutils.
(5) Switch all gcc's, nios2-gcc{3,41} to DEPENDS above (1) binutils.
(6) Delete nios2-binutils220 (2.20).