-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/sdlversion.d

@@ -0,0 +1,83 @@
+
+//          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.sdlversion;
+
+struct SDL_version {
+    ubyte major;
+    ubyte minor;
+    ubyte patch;
+}
+
+enum SDL_MAJOR_VERSION = 2;
+enum SDL_MINOR_VERSION = 0;
+
+version(SDL_201) {
+    enum ubyte SDL_PATCHLEVEL = 1;
+}
+else version(SDL_202) {
+    enum ubyte SDL_PATCHLEVEL = 2;
+}
+else version(SDL_203) {
+    enum ubyte SDL_PATCHLEVEL = 3;
+}
+else version(SDL_204) {
+    enum ubyte SDL_PATCHLEVEL = 4;
+}
+else version(SDL_205) {
+    enum ubyte SDL_PATCHLEVEL = 5;
+}
+else version(SDL_206) {
+    enum ubyte SDL_PATCHLEVEL = 6;
+}
+else version(SDL_207) {
+    enum ubyte SDL_PATCHLEVEL = 7;
+}
+else version(SDL_208) {
+    enum ubyte SDL_PATCHLEVEL = 8;
+}
+else version(SDL_209) {
+    enum ubyte SDL_PATCHLEVEL = 9;
+}
+else version(SDL_2010) {
+    enum ubyte SDL_PATCHLEVEL = 10;
+}
+else {
+    enum ubyte SDL_PATCHLEVEL = 0;
+}
+
+@nogc nothrow pure
+void SDL_VERSION(SDL_version* x) {
+    pragma(inline, true);
+    x.major = SDL_MAJOR_VERSION;
+    x.minor = SDL_MINOR_VERSION;
+    x.patch = SDL_PATCHLEVEL;
+}
+
+enum SDL_VERSIONNUM(ubyte X, ubyte Y, ubyte Z) = X*1000 + Y*100 + Z;
+enum SDL_COMPILEDVERSION = SDL_VERSIONNUM!(SDL_MAJOR_VERSION, SDL_MINOR_VERSION, SDL_PATCHLEVEL);
+enum SDL_VERSION_ATLEAST(ubyte X, ubyte Y, ubyte Z) = SDL_COMPILEDVERSION >= SDL_VERSIONNUM!(X, Y, Z);
+
+version(BindSDL_Static) {
+    extern(C) @nogc nothrow {
+        void SDL_GetVersion(SDL_version*);
+        const(char)* SDL_GetRevision();
+        int SDL_GetRevisionNumber();
+    }
+}
+else {
+    extern(C) @nogc nothrow {
+        alias pSDL_GetVersion = void function(SDL_version*);
+        alias pSDL_GetRevision = const(char)* function();
+        alias pSDL_GetRevisionNumber = int function();
+    }
+
+    __gshared {
+        pSDL_GetVersion SDL_GetVersion;
+        pSDL_GetRevision SDL_GetRevision;
+        pSDL_GetRevisionNumber SDL_GetRevisionNumber;
+    }
+}