(svn r12352) -Fix: Some callback-results were treated as 8 bit, when they were 15 bit, and vice versa.

Var 0x7E procedure-results are always 15 bit.
  Callbacks 0x2A, 0x2C, 0x36 (sometimes), 0x39 and 0x145 are 15 bit.
  Non-varaction2-calculated callback-results are also affected by the 8bit masking.

src/newgrf_callbacks.h

@@ -210,6 +210,11 @@ enum CallbackID {
 
 	/** Customize the output cargo types of a newly build industry. */
 	CBID_INDUSTRY_OUTPUT_CARGO_TYPES     = 0x14C,
+
+	/* ATTENTION:
+	 * When adding new callbacks and their result is 15bit, add them to newgrf_spritegroup.cpp:Is8BitCallback().
+	 * It does not harm to add them there though they are not implemented. But it does harm if they get forgotton.
+	 */
 };
 
 /**