Support keyboard remapping

[nmlgc]

The game does support remapping the joypad, after all. The InputConfig structure also suggests that keyboard remapping was even planned at some point in development:

ssg/DirectXUTYs/DI_UTY.CPP

Lines 54 to 73 in e6267e9

	IConfig.bIsUsed[DIK_ESCAPE] = TRUE;
	IConfig.bIsUsed[DIK_RETURN] = TRUE;
	IConfig.bIsUsed[DIK_UP] = TRUE;
	IConfig.bIsUsed[DIK_DOWN] = TRUE;
	IConfig.bIsUsed[DIK_LEFT] = TRUE;
	IConfig.bIsUsed[DIK_RIGHT] = TRUE;
	IConfig.KeyUp = DIK_NUMPAD8; IConfig.bIsUsed[DIK_NUMPAD8] = TRUE;
	IConfig.KeyDown = DIK_NUMPAD2; IConfig.bIsUsed[DIK_NUMPAD2] = TRUE;
	IConfig.KeyLeft = DIK_NUMPAD4; IConfig.bIsUsed[DIK_NUMPAD4] = TRUE;
	IConfig.KeyRight = DIK_NUMPAD6; IConfig.bIsUsed[DIK_NUMPAD6] = TRUE;
	IConfig.KeyULeft = DIK_NUMPAD7; IConfig.bIsUsed[DIK_NUMPAD7] = TRUE;
	IConfig.KeyURight = DIK_NUMPAD9; IConfig.bIsUsed[DIK_NUMPAD9] = TRUE;
	IConfig.KeyDLeft = DIK_NUMPAD1; IConfig.bIsUsed[DIK_NUMPAD1] = TRUE;
	IConfig.KeyDRight = DIK_NUMPAD3; IConfig.bIsUsed[DIK_NUMPAD3] = TRUE;
	IConfig.KeyTama = DIK_Z; IConfig.bIsUsed[DIK_Z] = TRUE;
	IConfig.KeyBomb = DIK_X; IConfig.bIsUsed[DIK_X] = TRUE;
	IConfig.KeyShift = DIK_LSHIFT; IConfig.bIsUsed[DIK_LSHIFT] = TRUE;

This would mostly be about adding the UI for it.