Fix warnings triggered by isle-portable (#1304)

* Replace computed constant with more readable computed constants

* LegoAnim::GetActorUnknown0x04 returns a number, not a pointer

* Add macro for creating RGB555 colors

* Texture pixel data is passed through as const data

* Compare palette index against 0 instead of NULL pointer

* warning: deleting 'void*' is undefined [-Wdelete-incomplete] warning

Some DirectX sdk's declars D3DRMIMAGE::buffer1 and D3DRMIMAGE::buffer2
as a void pointer.

* Don't use floats

* Fix wrong op

---------

Co-authored-by: Christian Semmler <mail@csemmler.com>

LEGO1/lego/sources/anim/legoanim.cpp

@@ -1163,7 +1163,7 @@ undefined4 LegoAnim::GetActorUnknown0x04(LegoU32 p_index)
 		return m_modelList[p_index].m_unk0x04;
 	}
 
-	return NULL;
+	return 0;
 }
 
 // FUNCTION: LEGO1 0x100a0f60