CharProxy: Add copy constructor
CharProxy: Add copy constructor

Adding the copy constructor is needed to solve a `-Wdeprecated-copy` warning
from GCC and Clang, which is raised when upgrading doctest from 2.4.4 to 2.4.6.

(cherry picked from commit cc57cbb73a4675f8b51e6cf4a77f0f9d814d4b01)

ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot