gdb: apply upstream patch to fix OS X crash

There is a known issue with gdb 7.4 on OS X where calling `run` on twice
in the same debugging session will crash gdb. It's been fixed upstream
and it's targeted for 7.5. I've added a patch that fixes it in the
formula.

The bug report:
http://old.nabble.com/-Bug-gdb-13619--New%3A-Crash-when-running-binary-a-second-time-in-the-same-session-td33196464.html
The patch (linked from the bug report):
http://sourceware.org/ml/gdb-patches/2012-02/msg00098.html

Closes Homebrew/homebrew#8.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

Formula/gdb.rb

@@ -8,6 +8,13 @@ class Gdb < Formula
 
   depends_on 'readline'
 
+  def patches
+    # patch to fix a crash when calling `run` twice in one session.  It is
+    # upstream in gdb 7.5 and should be removed at that point.
+    # http://old.nabble.com/-Bug-gdb-13619--New%3A-Crash-when-running-binary-a-second-time-in-the-same-session-td33196464.html
+    { :p0 => DATA }
+  end
+
   def install
     system "./configure", "--prefix=#{prefix}",
                           "--disable-debug",
@@ -26,3 +33,22 @@ class Gdb < Formula
     EOS
   end
 end
+
+__END__
+diff -c -r1.18 solib-darwin.c
+*** gdb/solib-darwin.c	4 Jan 2012 08:17:11 -0000	1.18
+--- gdb/solib-darwin.c	8 Feb 2012 09:15:49 -0000
+***************
+*** 456,461 ****
+--- 456,467 ----
+        error (_("`%s': not a shared-library: %s"),
+          found_pathname, bfd_errmsg (bfd_get_error ()));
+      }
++
++   /* Make sure that the filename is malloc'ed.  The current filename
++      for fat-binaries BFDs is a name that was generated by BFD, usually
++      a static string containing the name of the architecture.  */
++   res->filename = xstrdup (pathname);
++
+    return res;
+  }