Export watch_file.

Export watch_file, as this is the easiest API entry point between FileMonitor
and PollingFileMonitor.

Fix _uv_hook_fseventscb such that the condition is notified even if no callback
is in the monitor. Also fix the value sent to notify() to match the expected
return value in wait().

Fix watch_poll default callback.
Document watch_file method.
Add a test for wait(FileMonitor).
Unexport new UV_ constants.
WIP: File watching event refactor.
Re-passing tests.
Refactor events with integer flag fields and accessors.
Fix logic bug in FDWatcher wait()
fix #4264

was a type inference bug involving inner functions
check for null before using `loop` pointer in event loop runners in jl_uv.c
Merge branch 'watch-refactor' of https://github.com/blakejohnson/julia into jb/watch-refactor
my version of the file watching API refactor
WINDOWS: resource-definition script and an icon (generated by the Icon Composer including in XCode)
fix #4220
Merge branch 'master' of github.com:JuliaLang/julia
fix #4242
add DomainErrors to some bessel functions, part of #4187
allow converting SubString tails of ByteStrings to pointers

and return bytestrings from path functions, because that's probably what
will be needed in most cases.
fixes #4106
Added helpefull message for DomainError

Some functions throw DomainError for Real arguments because of type
stability and that the correct answer is complex. This patch add a ugly
hack, inspecting the bactrace, to give newcommers a helpefull hint. It
also document some of the functions that throws DomainError for negative
Real arguments.
update matlab differences
should fix #4277