AbstractFramebuffer: Always use bindImplementationSingle for WebGL

WebGL doesn't support anything else.

src/Magnum/AbstractFramebuffer.cpp

@@ -105,9 +105,13 @@ void AbstractFramebuffer::bind() {
 }
 
 void AbstractFramebuffer::bindInternal(FramebufferTarget target) {
-    #if defined(MAGNUM_TARGET_GLES2) && !defined(MAGNUM_TARGET_WEBGL)
+    #if defined(MAGNUM_TARGET_GLES2)
+    #if !defined(MAGNUM_TARGET_WEBGL)
     (this->*Context::current().state().framebuffer->bindImplementation)(target);
     #else
+    bindImplementationSingle();
+    #endif
+    #else
     bindImplementationDefault(target);
     #endif
 }
@@ -146,9 +150,13 @@ void AbstractFramebuffer::bindImplementationDefault(FramebufferTarget target) {
 }
 
 FramebufferTarget AbstractFramebuffer::bindInternal() {
-    #if defined(MAGNUM_TARGET_GLES2) && !defined(MAGNUM_TARGET_WEBGL)
+    #if defined(MAGNUM_TARGET_GLES2)
+    #if !defined(MAGNUM_TARGET_WEBGL)
     return (this->*Context::current().state().framebuffer->bindInternalImplementation)();
     #else
+    return bindImplementationSingle();
+    #endif
+    #else
     return bindImplementationDefault();
     #endif
 }