Platform: haha, Doxygen Markdown parser is broken here, haha!

Note to self: look at the docs at least once before copying a broken
markup all over the place.

src/Magnum/Platform/EmscriptenApplication.h

@@ -1338,7 +1338,7 @@ enum class EmscriptenApplication::Key: Int {
 
     /**
      * Plus. On the US keyboard layout this may only be representable as
-     * @m_class{m-label m-warning} **Shift** @m_class{m-label m-default} **=**.
+     * @m_class{m-label m-warning} **Shift** @m_class{m-label m-default} <b>=</b>.
      */
     Plus,
 

src/Magnum/Platform/GlfwApplication.h

@@ -1167,7 +1167,7 @@ enum class GlfwApplication::Key: Int {
 
     /**
      * Plus. On the US keyboard layout this may only be representable as
-     * @m_class{m-label m-warning} **Shift** @m_class{m-label m-default} **=**.
+     * @m_class{m-label m-warning} **Shift** @m_class{m-label m-default} <b>=</b>.
      */
     Plus = '+',
 

src/Magnum/Platform/Sdl2Application.h

@@ -1744,7 +1744,7 @@ enum class Sdl2Application::Key: SDL_Keycode {
 
     /**
      * Plus. On the US keyboard layout this may only be representable as
-     * @m_class{m-label m-warning} **Shift** @m_class{m-label m-default} **=**.
+     * @m_class{m-label m-warning} **Shift** @m_class{m-label m-default} <b>=</b>.
      */
     Plus = SDLK_PLUS,