Editor code: tidy up BOOLs,NULLs and overrides pt4.

A few 'typedefs' replaced by 'using's
This shouldn't have any functional changes at all, just c++17 modernization
It's a part 4 of a split #2847

Signed-off-by: Nemerle <nemerle5+git@gmail.com>

Code/Editor/Util/Math.h

@@ -128,7 +128,7 @@ inline float PointToLineDistance(const Vec3& p1, const Vec3& p2, const Vec3& p3,
     @param p2 Target point of first line.
     @param p3 Source point of second line.
     @param p4 Target point of second line.
-    @return FALSE if no solution exists.
+    @return false if no solution exists.
 */
 inline bool LineLineIntersect(const Vec3& p1, const Vec3& p2, const Vec3& p3, const Vec3& p4,
     Vec3& pa, Vec3& pb, float& mua, float& mub)