API change to remove dual loading default case for dac_load_data_buffer_single

Also change dac_data from u32 to u16
Removed examples, they are moved into libopencm3-examples repository.
Using while(1) instead of exit.

The exit function can significantly increase code size, and adds
dependency on stdlibc.
add 16MHz resonator for stm32f4
[stm32][f4] ld file for f405x6
Fixed dma interrupt flag related definitions.
Synchronise linker scripts which are supposed to be identical

This also report bug fixes about data alignment and bss storage to EFM32 &
LM3S targets.

Note: removed chrysn copyright statement as the file is a verbatim copy of
previous files.
Add support for static constructors and destructors
Small improvements of using FLASH memory in STM32F1XX
Remove redundant access size argument in F4 flash code.
Change the way buffer for control requests data is allocated

Current way of having a globally, but weakly defined static buffer has
several shortcomings:
 - It forces user to have a certain "magic" byte array variable if
   they want to have a control buffer of different size.
 - Having a globally defined static array and a separate function to
   tell USB core about its size is error prone.
 - Its inner workings are not easily understandable form cursory look
   at API and one needs to go and look at the implementation code to
   connect all the pieces into a solid picture of how it works

This commit adds two parameters to 'usbd_init' call that allow user to
specify the pointer to the area of memory and a size of that memory
which would be used by the USB core to store the data received during
DATA stage of control requests. This approach, while further
complicating the prototype of 'usbd_init', provides user with more
flexibility allowing for any custom area of memory of any size to be
used as control buffer. It also forces user to provide both address
and memory size at the same time thus avoiding the possibility of user
redefining 'usbd_control_buffer', but not calling
'usbd_set_control_buffer_size' after that.