base/linalg/lapack.jl: Import PosDefException
Merge pull request #6298 from mschauer/posdefex

base/linalg/lapack.jl: import PosDefException
remove help categories (closes #6294)
move list and tree examples to DataStructures

remove colorimetry, ndrange, and queue

use immutable in time example
Merge branch 'master' of github.com:JuliaLang/julia
accelerate backtrace-to-function mapping

this seems to make printing backtraces about 90% faster
fix bounds checking of findnext

`findnext(randn(10) .< 0.0, 0)` causes segmentation fault bacause
the start index 0 is out of bounds.
Merge pull request #6303 from bicycle1885/fix-findnext

fix bounds checking of findnext