First cut at changes discussed in issue #3423

This version also needs cleaning (the two cholfact methods defined in the loop should be condensed to one) but I am putting this up for others to see what I meant.
readdlm variant to accept memory mapped byte arrays.
updated docs for readdlm.
avoid bytestring buffercopy with jl_array_to_string
pkg2: rollback on resolve failure, better handling of unknown packages.
Implemented @fetch and @fetchfrom, the fetch versions of @spawn and @spawnat
Fix #3448
tunnel option supports sshflags
Fixed description of ``NULL`` vs R

Someone accidentally forgot a couple of words here. This adds the words back in.
Merge pull request #3452 from pridkett/patch-1

Fixed description of ``NULL`` in the comparison to R
Merge pull request #3451 from amitmurthy/amitm/tunnel

addprocs() tunnel option uses sshflags
Merge pull request #3442 from tanmaykm/readcsv

readdlm variant to accept memory mapped byte arrays.
Merge branch 'master' of github.com:JuliaLang/julia
convert(Rational, x::Float32) => Rational{Int32} on 32-bit platforms.

Pull-request #3447 has a different fix for this and some other issues.
Check for returned error values from libunwind.
Merge pull request #3463 from blakejohnson/backtrace-fix

Check for returned error values from libunwind in rec_backtrace
don't use reshape to show vectors
print whole vector for repr(vec), don't use ...
fixes #3362
Fix #3455, fix #3459, add more rsearch tests

Also
 * add a default definition for rsearch(s::String, c::Chars)
 * remove some redundant tests for search
 * fix some tests for search by using endof instead of length
fix #3446
update test/Makefile
Merge branch 'master' of github.com:JuliaLang/julia
fix #3464