-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/sdlassert.d

@@ -0,0 +1,70 @@
+
+//          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.sdlassert;
+
+import bindbc.sdl.config;
+
+enum SDL_assert_state : uint {
+    SDL_ASSERTION_RETRY = 0,
+    SDL_ASSERTION_BREAK = 1,
+    SDL_ASSERTION_ABORT = 2,
+    SDL_ASSERTION_IGNORE = 3,
+    SDL_ASSERTION_ALWAYS_IGNORE = 4
+}
+alias SDL_AssertState = SDL_assert_state;
+mixin(expandEnum!SDL_AssertState);
+
+struct SDL_assert_data {
+    int always_ignore;
+    uint trigger_count;
+    const(char) *condition;
+    const(char) *filename;
+    int linenum;
+    const(char) *function_;
+    const(SDL_assert_data) *next;
+}
+alias SDL_AssertData = SDL_assert_data;
+
+extern(C) nothrow alias SDL_AssertionHandler = SDL_AssertState function(const(SDL_AssertData)* data, void* userdata);
+
+version(BindSDL_Static) {
+    extern(C) @nogc nothrow {
+        void SDL_SetAssertionHandler(SDL_AssertionHandler,void*);
+        const(SDL_assert_data)* SDL_GetAssertionReport();
+        void SDL_ResetAssertionReport();
+
+        static if(sdlSupport >= SDLSupport.sdl202) {
+            SDL_AssertionHandler SDL_GetAssertionHandler(void**);
+            SDL_AssertionHandler SDL_GetDefaultAssertionHandler();
+        }
+    }
+}
+else {
+    extern(C) @nogc nothrow {
+        alias pSDL_SetAssertionHandler = void function(SDL_AssertionHandler,void*);
+        alias pSDL_GetAssertionReport = const(SDL_assert_data)* function();
+        alias pSDL_ResetAssertionReport = void function();
+    }
+
+    __gshared {
+        pSDL_SetAssertionHandler SDL_SetAssertionHandler;
+        pSDL_GetAssertionReport SDL_GetAssertionReport;
+        pSDL_ResetAssertionReport SDL_ResetAssertionReport;
+    }
+
+    static if(sdlSupport >= SDLSupport.sdl202) {
+        extern(C) @nogc nothrow {
+            alias pSDL_GetAssertionHandler = SDL_AssertionHandler function(void**);
+            alias pSDL_GetDefaultAssertionHandler = SDL_AssertionHandler function();
+        }
+
+        __gshared {
+            pSDL_GetAssertionHandler SDL_GetAssertionHandler;
+            pSDL_GetDefaultAssertionHandler SDL_GetDefaultAssertionHandler;
+        }
+    }
+}