Avoid some overflow situations in lcm and rational +, -, rem, mod.
make dump tolerate undefined fields. fixes #3386
jldownload: set more curl/fetch timeouts
Merge pull request #3382 from GunnarFarneback/rational

Avoid some rational overflow
Don't check PCRE subjects for UTF8 validity.
Merge branch 'master' of github.com:JuliaLang/julia into jb/conditionvars