c/5582: warn about using the extension "int x=x;"

[bangerth@dealii.org]

Old Synopsis: a warning to implement
New Synopsis: warn about using the extension "int x=x;"

State-Changed-From-To: open->analyzed
State-Changed-By: bangerth
State-Changed-When: Tue Jan  7 17:12:05 2003
State-Changed-Why:
    The use of
      int x = x;
    is a gcc extension, but I could indeed not find a place in
    the manual that talks about a warning option that gives
    a message when this extension is used.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=5582