Delete directx-devel package and SDL2 dependency on it.

This version of the DirectX headers from the SDL website is woefully
out of date and in fact is even missing a bunch of types that are
necessary to build SDL. They seem to be unnecessary anyway since
mingw-64 includes newer versions of them anyway.

Fixes #21.

pkgdef/SDL2.sh

@@ -16,12 +16,6 @@ if [ $(uname) = "Darwin" ]; then
     config_options+=" --disable-video-x11"
 fi
 
-# When targeting Windows, we need to install the directx headers first.
-if [ $(uname) = "Cygwin" ] || [[ "$BUILD_HOST" = *mingw* ]]; then
-    dependencies directx-devel
-    config_options+=" --disable-directx"
-fi
-
 # Disable assembly to avoid depending on SIMD stuff.
 if [[ "$BUILD_HOST" = *-*-emscripten ]]; then
     config_options+=" --disable-assembly"

pkgdef/directx-devel.sh

@@ -1,12 +0,0 @@
-description "Extra header files for compiling DirectX applications"
-fetch_download https://www.libsdl.org/extras/win32/common/directx-devel.tar.gz \
-               75595621b9e3da390435cbc762bd7f24f711ef06b3338a34e350622da624b360
-IS_TAR_BOMB=true
-
-do_build() {
-    true
-}
-
-do_install() {
-    cp -R include lib "$PACKAGE_INSTALL_DIR"
-}