Add patch for GCC bug 58800.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58800

I have not been able to test this due to nix wanting to rebuild lots of things before building gcc.
Patch was created with: `svn diff -r 203872:203873 http://gcc.gnu.org/svn/gcc/branches`

This should fix a crash in OpenSCAD: https://github.com/openscad/openscad/issues/514