Global: Remove temporary backup files

file.c~ (note the tilde at the end) are temporary backup files used by some
editors. They are not needed.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
[lm4f] Added a note for Windows users to the README
[stm32x] Use modern header include paths.

Replace includes of stm32/YY/xxxx.h with stm32/xxxx.h
Replace stm32/YY/nvic.h with cm3/nvic.h.
In some cases, the include list was resorted alphabetically when it was
complicated and I was reviewing them manually, but most of this was
automatically done.
[BUILD] Paralelize cleaning of examples

make clean     1:50 -> 1:55 (no change)
make clean -j8 1:30 -> 0:28 (strongly faster)

Measured on Core i7 (4 cores, each HT) @ 3GHz