libsdl: config tweaks, remove sdlmain lib

This patch contains changes to the libSDL port that were needed to build
the Hatari emulator using cmake.

- Since SDL programs cannot use the posix library (because sdl's init
  function needs a way to get hold of the Genode env), the sdl_main
  library must be used instead of the posix library. The sdl_main
  code implements the Libc::Component::construct function for the
  final binary. However, 3rd-party build systems are not aware of this
  Genode-specific peculiarity and thereby create binaries that leave
  libsdl uninitialized. This patch adds the sdl_main to libsdl by
  default and thereby eliminates the need for specifying the extra
  sdl_main library. Customizing the Libc::Component::construct is
  still possible by overriding the library-provided implementation
  in the main program.

- A few missing config definitions are added to compile Hatari
  successfully.

- Avoid reliance on the include/SDL convention in SDL_config.h

- Cmake relies on the upper-case naming of the library with no way
  to tweak this convention. So we install an symlink named `SDL.lib.so`
  when installing the library into the <build-dir>/bin/ directory.

Fixes #161

recipes/api/sdl/content.mk

@@ -1,9 +1,8 @@
 MIRROR_FROM_REP_DIR := lib/symbols/sdl lib/import/import-sdl.mk \
-                       lib/mk/sdlmain.mk
 
 MIRROR_FROM_LIBPORTS := lib/mk/mesa_api.mk
 
-content: $(MIRROR_FROM_REP_DIR) $(MIRROR_FROM_LIBPORTS) src/lib/sdl include LICENSE
+content: $(MIRROR_FROM_REP_DIR) $(MIRROR_FROM_LIBPORTS) include LICENSE
 
 $(MIRROR_FROM_REP_DIR):
 	$(mirror_from_rep_dir)
@@ -25,9 +24,5 @@ include:
 	cp -r $(MESA_PORT_DIR)/include/* $@/
 	cp -r $(GENODE_DIR)/repos/libports/include/EGL $@/
 
-src/lib/sdl:
-	mkdir -p $@
-	cp -r $(REP_DIR)/src/lib/sdl/sdl_main.cc $@/
-
 LICENSE:
 	cp $(SDL_PORT_DIR)/src/lib/sdl/COPYING $@

recipes/api/sdl/hash

@@ -1 +1 @@
-2018-03-18 2cdaa5c32a93a5acf0ee7159f96e9f01d67ab8d2
+2019-05-14 cb3175a6545ea045864baa9783f4ac54a3206826

recipes/src/sdl/hash

@@ -1 +1 @@
-2019-01-02 155b546298117fca760a633abcd79080e124df6c
+2019-05-14 598e91be62c73d18bad160f5f2438a855c4f0ed1