-improved WASM compilation scripts

-added external bindbc.sdl import for WASM
-working on demos (WIP, working simple demo with ECS and SDL2)
-small change in ecs.std

demos/external/imports/bindbc/sdl/bind/sdlgesture.d

@@ -0,0 +1,36 @@
+
+//          Copyright Michael D. Parker 2018.
+// Distributed under the Boost Software License, Version 1.0.
+//    (See accompanying file LICENSE_1_0.txt or copy at
+//          http://www.boost.org/LICENSE_1_0.txt)
+
+module bindbc.sdl.bind.sdlgesture;
+
+import bindbc.sdl.bind.sdltouch : SDL_TouchID;
+import bindbc.sdl.bind.sdlrwops : SDL_RWops;
+
+alias SDL_GestureID = long;
+
+version(BindSDL_Static) {
+    extern(C) @nogc nothrow {
+        int SDL_RecordGesture(SDL_TouchID);
+        int SDL_SaveAllDollarTemplates(SDL_RWops*);
+        int SDL_SaveDollarTemplate(SDL_GestureID,SDL_RWops*);
+        int SDL_LoadDollarTemplates(SDL_TouchID,SDL_RWops*);
+    }
+}
+else {
+    extern(C) @nogc nothrow {
+        alias pSDL_RecordGesture = int function(SDL_TouchID);
+        alias pSDL_SaveAllDollarTemplates = int function(SDL_RWops*);
+        alias pSDL_SaveDollarTemplate = int function(SDL_GestureID,SDL_RWops*);
+        alias pSDL_LoadDollarTemplates = int function(SDL_TouchID,SDL_RWops*);
+    }
+
+    __gshared {
+        pSDL_RecordGesture SDL_RecordGesture;
+        pSDL_SaveAllDollarTemplates SDL_SaveAllDollarTemplates;
+        pSDL_SaveDollarTemplate SDL_SaveDollarTemplate;
+        pSDL_LoadDollarTemplates SDL_LoadDollarTemplates;
+    }
+}