Add more RTC functions and an RTC example.

Thanks Lord James <lordjames@y7mail.com> for the patch!

examples/other/rtc/README

@@ -0,0 +1,43 @@
+------------------------------------------------------------------------------
+README
+------------------------------------------------------------------------------
+
+This is a small RTC example project.
+
+
+Building
+--------
+
+ $ make
+
+Running 'make' on the top-level libopenstm32 directory will automatically
+also build this example. Or you can build the library "manually" and
+then run 'make' in this directory.
+
+You may want to override the toolchain (e.g., arm-elf or arm-none-eabi):
+
+ $ PREFIX=arm-none-eabi make
+
+For a more verbose build you can use
+
+ $ make V=1
+
+
+Flashing
+--------
+
+You can flash the generated code using OpenOCD:
+
+ $ make flash
+
+Or you can do the same manually via:
+
+ $ openocd -f interface/jtagkey-tiny.cfg -f board/olimex_stm32_h103.cfg
+ $ telnet localhost 4444
+ > reset halt
+ > flash write_image erase rtc.hex
+ > reset
+
+Replace the "jtagkey-tiny.cfg" with whatever JTAG device you are using, and/or
+replace "olimex_stm32_h103.cfg" with your respective board config file.
+