allow pcre to handle substrings directly. fix #4015
Updated documentation

* Describe func!(x) convention for functions which modify their arguments
* Add brief introduction to standard library
* Fix up a few links
Merge pull request #4017 from JuliaLang/kms/func_mod_arg_doc

Updated documentation (fixes #4013)
allow cleanly having multiple copies of llvm builds
Add abstractions for working with Array view types (like SubArray)
"make testall1" runs all tests with a single core
Performance tip: Avoid abstract type parameterization of composite types
Added mark/reset to IOStream, IOBuffer, and AsyncStream
Also added show() for IOBuffer.