change which to return rather than show
improve ability to use require from sysimg.jl
Merge pull request #5666 from JuliaLang/jn/sysimg_using

improve ability to use require from sysimg.jl
add UndefVarError type for undefined variable errors
use a convention for renamed variables to allow better reporting of the names of undefined variables. fixes #5692
Merge pull request #5646 from WestleyArgentum/which

change which to return rather than show
remove whicht, update doc for methods() and which()
One more relaxation of test bounds in linalg.
Merge pull request #5705 from mschauer/linalg

One more relaxation of test bounds in linalg.
Update base.rst
Merge pull request #5707 from mbauman/patch-1

Doc: repr uses showall, not show