Add def to avoid double STB implementation#5

kerautret wants to merge 1 commit intoDGtal-team:mainDGtal-team/DGtal-Tutorials-DGMM2022:mainfrom

kerautret:Fix-double-declaration-STBImagekerautret/DGtal-Tutorials-DGMM2022:Fix-double-declaration-STBImageCopy head branch name to clipboard