D bindings: Mark enum conversion functions nothrow @nogc pure @safe (#3272)

* Fix error in dynamic version of D bindings

Dazed and confused but trying to continue

* Fix dispatch_indirect still using uint16_t in bgfx.idl

* D bindings: Mark enum conv. functions `nothrow @nogc pure @safe`

scripts/bindings-d.lua

@@ -749,7 +749,7 @@ extern(C++, "bgfx") package final abstract class %s{
 		
 		if typ.helper then
 			yield(string.format(
-				"%s_ to%s(%s v){ return (v << %s) & %s; }",
+				"%s_ to%s(%s v) nothrow @nogc pure @safe{ return (v << %s) & %s; }",
 				typeName,
 				typeName,
 				enumType,