As best as I can tell, the copy of tinyxml dfhack uses is unmodified
from whenever it was first bundled. This commit adds an option to CMake,
EXTERNAL_TINYXML, that if set to ON, will attempt to link against a system
tinyxml instead of using the dfhack-bundled one. It defaults to OFF,
so there is no change in default behavior.
The DFHACK_TINYXML variable is then set to either "tinyxml" or "dfhack-tinyxml"
so the library (and any plugins that need updating) can link against one
or the other.
The FindTinyXML.cmake script was taken from https://github.com/ros/cmake_modules
(licensed under the 3-clause BSD license).
Add license text to new CMake file.
Ben Rosser