Godot 1.0 was developed at a time where compilers defaulted to C++98.
Also disable `-Wall` on debug builds, there are now hundreds of warnings
from newer compilers that would need to be fixed.
This would best be done by adding a new `warnings` SCons option, which would
also affect non-debug builds, but I have no intention to fix warnings in the
1.0 branch, the goal here is just to get it to compile for archival and game
preservation.
(cherry picked from commit a68e96b8c2)
