Enable SDL thread support

This patch enables the use of threads and locking mechanisms in SDL
applications. The 'pthread' libary is used as backend. Not all features
are currently supported.

Fixes #185.

libports/lib/mk/sdl.mk

@@ -22,6 +22,7 @@ SRC_CC   = SDL_genode_fb_video.cc \
 
 INC_DIR += $(REP_DIR)/include/SDL \
            $(REP_DIR)/src/lib/sdl \
+           $(REP_DIR)/src/lib/sdl/thread \
            $(REP_DIR)/src/lib/sdl/video
 
 # main files
@@ -43,8 +44,10 @@ SRC_C   += SDL_getenv.c \
 # thread subsystem
 SRC_C   += SDL_thread.c \
            SDL_systhread.c \
+           SDL_syscond.c \
            SDL_sysmutex.c \
            SDL_syssem.c
+INC_DIR += $(SDL_DIR)/src/thread
 
 # cpuinfo subsystem
 SRC_C   += SDL_cpuinfo.c
@@ -101,7 +104,7 @@ SRC_C   += SDL_joystick.c \
 INC_DIR += $(SDL_DIR)/src/joystick
 
 # we need libc
-LIBS = libc
+LIBS = libc pthread
 
 # dim build noise for contrib code
 CC_OPT_SDL_RLEaccel += -Wno-unused-but-set-variable
@@ -114,6 +117,9 @@ vpath %    $(REP_DIR)/src/lib/sdl
 vpath %    $(REP_DIR)/src/lib/sdl/video
 
 # contribution pathes
+vpath SDL_syscond.c   $(SDL_DIR)/src/thread/generic
+vpath SDL_sysmutex.c  $(SDL_DIR)/src/thread/generic
+
 vpath %.c  $(SDL_DIR)/src
 vpath %.c  $(SDL_DIR)/src/stdlib
 vpath %.c  $(SDL_DIR)/src/video
@@ -121,7 +127,7 @@ vpath %.c  $(SDL_DIR)/src/video/dummy
 vpath %.c  $(SDL_DIR)/src/audio
 vpath %.c  $(SDL_DIR)/src/audio/dummy
 vpath %.c  $(SDL_DIR)/src/thread
-vpath %.c  $(SDL_DIR)/src/thread/generic
+vpath %.c  $(SDL_DIR)/src/thread/pthread
 vpath %.c  $(SDL_DIR)/src/timer
 vpath %.c  $(SDL_DIR)/src/timer/dummy
 vpath %.c  $(SDL_DIR)/src/events

libports/src/lib/sdl/SDL_config_genode.h

@@ -50,8 +50,8 @@
 /* Enable the stub shared object loader (src/loadso/dummy/\*.c) */
 #define SDL_LOADSO_DISABLED 1
 
-/* Enable the stub thread support (src/thread/generic/\*.c) */
-#define SDL_THREADS_DISABLED 1
+/* Enable thread support */
+#define SDL_THREAD_PTHREAD 1
 
 /* Enable dummy timer support */
 #define SDL_TIMER_DUMMY 1