-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/sdlpower.d

@@ -0,0 +1,33 @@
+
+//          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.sdlpower;
+
+import bindbc.sdl.config;
+
+enum SDL_PowerState {
+    SDL_POWERSTATE_UNKNOWN,
+    SDL_POWERSTATE_ON_BATTERY,
+    SDL_POWERSTATE_NO_BATTERY,
+    SDL_POWERSTATE_CHARGING,
+    SDL_POWERSTATE_CHARGED
+}
+mixin(expandEnum!SDL_PowerState);
+
+version(BindSDL_Static) {
+    extern(C) @nogc nothrow {
+        SDL_PowerState SDL_GetPowerInfo(int*,int*);
+    }
+}
+else {
+    extern(C) @nogc nothrow {
+        alias pSDL_GetPowerInfo = SDL_PowerState function(int*,int*);
+    }
+
+    __gshared {
+        pSDL_GetPowerInfo SDL_GetPowerInfo;
+    }
+}