Defines +,- for Triangular matrices

Fix #5927
Merge pull request #7627 from ronisbr/master

New version of mingw64-libexpat
Quick fix to metaprogramming.rst
Merge pull request #7629 from kersulis/patch-1

Quick fixes to metaprogramming.rst
parse ¬ (\neg) as a prefix operator
Merge pull request #7630 from stevengj/neg

parse ¬ (\neg) as a prefix operator
Add a brief explanation of n:n-1 as an index

Update splice! docs to describe insertion without removal of any elements.
Merge pull request #7631 from JuliaLang/kms/doc_empty_range_as_index

Add a brief explanation of n:n-1 as an index
Don't be so picky about patchelf version, as there are now newer versions floating around
Fix type inference for \
add some precompile items to help Pkg.update speed
In Makefiles, use $(shell which ...) not $(which ...)
call update_all_fptrs earlier, to avoid some redundant compilation
Change code_lowered to take Callable instead of Function. Fixes #7636.
Fix minor mistake in put! help entry

The help entry for `put!` refers to `take`, which was renamed `take!`
in commit f017133. This commit updates the reference to `take!`.
Merge pull request #7637 from grayclhn/patch-1

Fix minor mistake in put! help entry
We seem to have exceeded a magical size threshold for creating .dmg's

We must now pass the -size parameter explicitly.  Let's hope we never go over 200m, or we may have to increase this number again
Fix sumabs and sumabs2 for Complex

- BLAS.asum does not compute sum(abs(x)) for complex x.
- BLAS.dot is not defined for Complex. BLAS.dotc still seems to be a
  bit faster than the pure Julia implementation.
fix typo in performance tips (thanks to Comer Duncan on the mailing list)
update helpdb.jl