promote(::MathConst, ::Rational) => Rational.

This gives the exact rational value of the float approximation,
which is probably not the best possible rational approximaion of
constants like pi or e, but this is a decent first cut.
optimize Complex +/- Real
Merge pull request #3379 from stevengj/master

optimize Complex +/- Real
Add truncate and stat for FS.File
Add rsearch
Avoid some overflow situations in lcm and rational +, -, rem, mod.
work in progress fixing let
Merge branch 'master' of github.com:JuliaLang/julia into jb/conditionvars
IP Address parsing/printing
use Condition for stream and process
remove the filter argument from wait(). this simplifies things a lot.
Merge branch 'master' of github.com:JuliaLang/julia into jb/conditionvars
make dump tolerate undefined fields. fixes #3386
jldownload: set more curl/fetch timeouts
Merge pull request #3382 from GunnarFarneback/rational

Avoid some rational overflow
Reorganize stream server code
Fix bug in listen/accept
Don't check PCRE subjects for UTF8 validity.
fix some typos
restore the try block for catching EOF and deserialization errors. this
allows workers to exit when the head node quits (usually).
print errors in multi.jl to stderr
fix a couple extra problems, make tests pass
Merge branch 'master' of github.com:JuliaLang/julia into jb/conditionvars