Refactor: ModRM Handler replaced with compile-time lookup table.

Started refactoring to a library-based model to easily integrate
comprehensive unit testing. Added CPU exception handling system for
the GUI. Non-critical exceptions (though critical to execution of
emulated application) will not shutdown the application in the future
releases. Refactored Userspace::Run() logic so that the GUI-controls
reflect emulator behavior.

CMakeLists.txt

@@ -3,11 +3,12 @@ project(emulator C CXX)
 
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
-set(CMAKE_CXX_STANDDARD 23)
+set(CMAKE_CXX_STANDARD 26)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 
 add_subdirectory(external/glfw)
+add_subdirectory(external/gtest)
 
 if(CMAKE_BUILD_TYPE STREQUAL "Debug")
     add_compile_definitions(Debug)
@@ -39,3 +40,5 @@ target_include_directories(emulator PRIVATE external/glfw/include
 					    external/imgui
 					    external/imgui_club/imgui_memory_editor
 					    )
+
+add_subdirectory(tests)