API BREAKER: Replacing defines in irrTypes.h which are conflicting with c++ reserved identifier rules.

C++ has undefined behavior for identifiers starting with __ or with _ followed by an uppercase letter.
We still have many more (in IrrCompileConfig.h and in all header-guards), will likely replace those later as well.
As a workaround for users which might use irrlicht defines in their code, I've added the header irrLegacyDefines.h
Including that allows to continue using old defines for a while - or make it easier to have code which compiles 
with old and new Irrlicht library versions.


git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@6251 dfc29bdd-3216-0410-991c-e03cc46cb475

changes.txt

@@ -1,5 +1,9 @@
 --------------------------
 Changes in 1.9 (not yet released)
+- Many defines changed because they were using names which are reserved identifiers in c++.
+  Mostly it's about replacing __IRRxxx or _IRRxxx identifiers by versions without underscores
+  Sometimes underscores at end also got removed.
+  There is a header file irrLegacyDefines.h which can be included to allow having the old defines back.
 - Add equals and set_data functions to core::array for easier working with blocks of data.
 - SIrrlichtCreationParameters::IgnoreInput set to false works again on X11. 
   Thanks @ Victor Gaydov for report + patch + very good test cases! (bug #401)
@@ -3908,7 +3912,7 @@ Changes in version 0.12.0 (24 August 2005)
 
 - Changed the names the driver return (now "OpenGL 1.5", "Direct3D 9.0" and "Direct3D 8.1")
 
-- Added a new macro _IRR_DEBUG_BREAK_IF which is now used instead of the _asm int 3 break points in
+- Added a new macro IRR_DEBUG_BREAK_IF which is now used instead of the _asm int 3 break points in
   debug mode.
 
 - Fixed a bug were the software renderer didn't clip 2d rectangles. This effect was visible for