Support GCC version "4.7" in LinBox

Imported from <a href="http://trac.sagemath.org/sage_trac/ticket/13118">trac #13118</a>.

linbox error on rackspace.com virtual machine, ubuntu 12

Reported by: jdemeyer

Component: packages

CC: 

Report Upstream: N/A

Authors: Jeroen Demeyer

Dependencies: 

Work issues: 

Reviewers: R. Andrew Ohana

Merged in: sage-5.1.beta6

Attachments: <ol><li><a href="http://trac.sagemath.org/sage_trac/attachment/ticket/13118/linbox-1.1.6.p11.diff">linbox-1.1.6.p11.diff: Diff for the linbox spkg. For reference / review only.</a> by jdemeyer at 20120618T22:34:01</li><li><a href="http://trac.sagemath.org/sage_trac/attachment/ticket/13118/here.txt">here.txt: linbox error on rackspace.com virtual machine, ubuntu 12</a> by startakovsky at 20121029T22:47:28</li></ol>