Proposed deduplication of peripherals, GPIO example

See rambling post on dev list for justification

lib/stm32/f2/Makefile

@@ -28,9 +28,10 @@ CFLAGS		= -Os -g -Wall -Wextra -I../../../include -fno-common \
 		  -ffunction-sections -fdata-sections -MD -DSTM32F2
 # ARFLAGS	= rcsv
 ARFLAGS		= rcs
-OBJS		= rcc.o gpio2.o usart.o spi.o flash.o \
-		  i2c.o exti2.o timer.o
+OBJS		= rcc.o gpio.o usart.o spi.o flash.o \
+		  i2c.o exti2.o timer.o \
+		  gpio_common_all.o gpio_common_f24.o
 
-VPATH += ../../usb:../:../../cm3
+VPATH += ../../usb:../:../../cm3:../common
 
 include ../../Makefile.include

lib/stm32/f2/gpio.c

@@ -0,0 +1,28 @@
+/** @defgroup gpio_file GPIO
+
+@ingroup STM32F2xx
+
+@brief <b>libopencm3 STM32F2xx General Purpose I/O</b>
+
+*/
+
+/*
+ * This file is part of the libopencm3 project.
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/stm32/common/gpio_common_f24.h>
+