revise the license terms
README: update verified toolchain list
improve the descriptions about external sources
start: replace init_*_seg with memset/memcpy
Merge pull request #95 from rampant1018/master

start: replace init_*_seg with memset/memcpy
entry: replace init_*_seg with memcpy/memset
Merge pull request #96 from rampant1018/master

loader: replace init_*_seg with memcpy/memset
Merge remote-tracking branch 'origin/master' into stm32-p103