Fix a number of top level doxygen issues.

So that the navigation pane works correctly in browsers.
Some additional doc fixes put in where found (but many more still to go).
Added some dummy .c and .h files to bring the associated docs into line.
makefile changed to allow 'make html' as well as 'make doc' (the latter only does html anyway).

lib/stm32/common/exti_common_all.c

@@ -20,6 +20,8 @@
  * This provides the code for the "next gen" EXTI block provided in F2/F4/L1
  * devices.  (differences only in the source selection)
  */
+/**@{*/
+
 
 #include <libopencm3/stm32/memorymap.h>
 #include <libopencm3/stm32/exti.h>
@@ -149,3 +151,5 @@ void exti_select_source(uint32_t exti, uint32_t gpioport)
 #endif
 	};
 }
+/**@}*/
+

lib/stm32/common/flash_common_f234.c

@@ -21,6 +21,7 @@
  * 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/>.
  */
+/**@{*/
 
 /**@{*/
 

lib/stm32/common/flash_common_f24.c

@@ -21,6 +21,7 @@
  * 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/>.
  */
+/**@{*/
 
 /**@{*/
 

lib/stm32/common/hash_common_f24.c

@@ -1,13 +1,13 @@
 /** @addtogroup hash_file
-
-@author @htmlonly © @endhtmlonly 2013
-Mikhail Avkhimenia <mikhail@avkhimenia.net>
-
-This library supports the HASH processor in the STM32F2 and STM32F4
-series of ARM Cortex Microcontrollers by ST Microelectronics.
-
-LGPL License Terms @ref lgpl_license
- */
+ *
+ * @author @htmlonly &copy; @endhtmlonly 2013
+ * Mikhail Avkhimenia <mikhail@avkhimenia.net>
+ *
+ * This library supports the HASH processor in the STM32F2 and STM32F4
+ * series of ARM Cortex Microcontrollers by ST Microelectronics.
+ *
+ * LGPL License Terms @ref lgpl_license
+ *  */
 
 /*
  * This file is part of the libopencm3 project.
@@ -159,3 +159,5 @@ void hash_get_result(uint32_t *data)
 		data[4] = HASH_HR[4];
 	}
 }
+/**@}*/
+

lib/stm32/common/rcc_common_all.c

@@ -17,6 +17,7 @@
  * 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/rcc.h>
 
@@ -181,6 +182,7 @@ void rcc_periph_reset_release(enum rcc_periph_rst rst)
 {
 	_RCC_REG(rst) &= ~_RCC_BIT(rst);
 }
+/**@}*/
 
 #undef _RCC_REG
 #undef _RCC_BIT