Some more file/path restructuring.

All #includes now explicitly use the "<libopencm3/stm32/rcc.h>" format.
If you want to get rid of the "libopencm3" prefix in your local project you
can add a respective -I entry in your Makefile (not recommended though).

All .ld files and .a libs are installed in $(TOOLCHAIN_DIR)/lib
directly (as before), but are now renamed to avoid potential
conflicts now or in the future. Examples:

  libopencm3_lpc13xx.a
  libopencm3_lpc13xx.ld
  libopencm3_stm32.a
  libopencm3_stm32.ld

lib/stm32/timer.c

@@ -25,7 +25,7 @@
  *                 TIM_CR1_CMS_CENTRE_3, TIM_CR1_DIR_UP);
  */
 
-#include <stm32/timer.h>
+#include <libopencm3/stm32/timer.h>
 
 void timer_set_mode(u32 timer_peripheral, u8 clock_div, u8 alignment,
 		    u8 direction)