Update CImg to v.3.7.4

Update CImg to v.3.7.2

Update CImg to v.3.6.6

fix(makefile): remove -fpermissive

chore(lib): document API, BITMAPS[]

fix: move sqr(n) from library to driver

Merge remote-tracking branch 'refs/remotes/origin/master'

Update CImg to v.3.6.4

Update CImg to v.3.6.3

Update CImg to v.3.6.2

Update CImg to v.3.6.1

Update CImg to v.3.5.5

Update CImg to v.3.5.4

Update CImg to v.3.5.3

Update CImg to v.3.5.2