Fix #7551

Simply drop out of search mode (back to the original mode) when accepting an empty search-string.
Remove outdated size tweak from performance tips section of manual
fix some typos in the cholmod wrappers
add missing $s in cholmod
changes to Base to make it easier to statically compile

some fixes and cleanups in umfpack wrappers

Conflicts:

	base/fftw.jl
Merge pull request #7562 from JuliaLang/sjk/perf-tips

Remove outdated size tweak from performance tips section of manual
add conversion from SubArray to Ptr{None}
Merge branch 'master' of github.com:JuliaLang/julia
fix #7564

this is a combination of convert(Rational{T},x) not returning the
correct type, and the lack of a type check in codegen for new().
fix gemv! and gemm! in empty cases. fixes #7571

should always mutate, not sometimes return a new array
update helpdb
Update NEWS.md

Includes missing cross-references and minor formatting changes.
remove 0.2 deprecations and update one old precompile directive.
Add faster cumsum and cumprod to NEWS.
update help for nnz
Merge branch 'master' of github.com:JuliaLang/julia
add clear() function that replaces Main

a link to the previous Main called LastMain is provided.
`using LastMain.Package` works to restore access to loaded libraries.

fixes #1195, fixes #2385
return nothing from clear()
NEWS and documentation for `clear`
fix recent mistake in type checking for new()