Add Xbox OG support

Makefile

@@ -40,6 +40,15 @@ endif
 
 CC_AS ?= $(CC)
 
+SPACE :=
+SPACE := $(SPACE) $(SPACE)
+BACKSLASH :=
+BACKSLASH := \$(BACKSLASH)
+filter_out1 = $(filter-out $(firstword $1),$1)
+filter_out2 = $(call filter_out1,$(call filter_out1,$1))
+unixpath = $(subst \,/,$1)
+unixcygpath = /$(subst :,,$(call unixpath,$1))
+
 ifeq ($(platform), unix)
    TARGET := $(TARGET_NAME)_libretro.so
    fpic := -fPIC
@@ -286,6 +295,22 @@ LDFLAGS += -DLL
 CFLAGS += -D_CRT_SECURE_NO_DEPRECATE
 LIBS =
 
+# Windows MSVC 2003 Xbox 1
+else ifeq ($(platform), xbox1_msvc2003)
+TARGET := $(TARGET_NAME)_libretro_xdk1.lib
+CC  = CL.exe
+CXX  = CL.exe
+LD   = lib.exe
+AR   = lib.exe
+
+export INCLUDE := $(XDK)/xbox/include
+export LIB := $(XDK)/xbox/lib
+PATH := $(call unixcygpath,$(XDK)/xbox/bin/vc71):$(PATH)
+PSS_STYLE :=2
+CFLAGS   += -D_XBOX -D_XBOX1
+CXXFLAGS += -D_XBOX -D_XBOX1
+STATIC_LINKING=1
+
 # Windows MSVC 2003 x86
 else ifeq ($(platform), windows_msvc2003_x86)
 	CC  = cl.exe

Makefile.common

+LIBRETRO_COMM_DIR  = $(CORE_DIR)/libretro-common
+
 INCFLAGS := \
 	-I$(CORE_DIR) \
-	-I$(CORE_DIR)/libretro-common/include \
+	-I$(LIBRETRO_COMM_DIR)/include \
 	-I$(EMULIB) \
 	-I$(LIBZ80) \
 	-I$(FMSXDIR)
 
+ifneq (,$(findstring msvc2003,$(platform)))
+INCFLAGS += -I$(LIBRETRO_COMM_DIR)/include/compat/msvc
+endif
+
 COREDEFINES := -DUNIX -DFMSX -DBPS16 -DBPP16
 
 ifeq ($(PATCH_Z80), 1)