split out device-specific recovery UI code into vendor directories

Take some device-specific details of the recovery UI (eg, what keys to
press to bring up the interface and perform actions, exact text of the
menu, etc.) and split them out into separate C functions.  Arrange to
take implementations of those functions from the appropriate vendor
directory at build time.  Provide a default implementation in case no
vendor-specific one is available.

Android.mk

@@ -1,11 +1,11 @@
+ifneq ($(TARGET_SIMULATOR),true)
+ifeq ($(TARGET_ARCH),arm)
+
 LOCAL_PATH := $(call my-dir)
 include $(CLEAR_VARS)
 
 commands_recovery_local_path := $(LOCAL_PATH)
 
-ifneq ($(TARGET_SIMULATOR),true)
-ifeq ($(TARGET_ARCH),arm)
-
 LOCAL_SRC_FILES := \
 	recovery.c \
 	bootloader.c \
@@ -29,17 +29,22 @@ LOCAL_FORCE_STATIC_EXECUTABLE := true
 
 LOCAL_MODULE_TAGS := eng
 
-LOCAL_STATIC_LIBRARIES := libminzip libunz libamend libmtdutils libmincrypt
+LOCAL_STATIC_LIBRARIES :=
+ifeq ($(TARGET_RECOVERY_UI_LIB),)
+  LOCAL_SRC_FILES += default_recovery_ui.c
+else
+  LOCAL_STATIC_LIBRARIES += $(TARGET_RECOVERY_UI_LIB)
+endif
+LOCAL_STATIC_LIBRARIES += libminzip libunz libamend libmtdutils libmincrypt
 LOCAL_STATIC_LIBRARIES += libminui libpixelflinger_static libpng libcutils
 LOCAL_STATIC_LIBRARIES += libstdc++ libc
 
 include $(BUILD_EXECUTABLE)
 
-include $(commands_recovery_local_path)/minui/Android.mk
-
 endif   # TARGET_ARCH == arm
 endif	# !TARGET_SIMULATOR
 
+include $(commands_recovery_local_path)/minui/Android.mk
 include $(commands_recovery_local_path)/amend/Android.mk
 include $(commands_recovery_local_path)/minzip/Android.mk
 include $(commands_recovery_local_path)/mtdutils/Android.mk