Fix a bunch of typos: syced -> synced

This commit is the result of running this command in src/ directory:
git grep -lz 'syced' | xargs -0 perl -i'' -pE "s/syced/synced/g"

Thank you stackoverflow :)
http://stackoverflow.com/questions/1583219/awk-sed-how-to-do-a-recursive-find-replace-of-a-string

(I used the "git safe" version)