MySQL: allow compilation with Xcode-only setups

Closes #20185.
Add Enumerable#group_by
Merge repeated deps with differing options

When expanding dependencies, repeated deps are treated as equal and all
but the first are discarded when #uniq is called on the resulting array.
However, they may have different sets of options attached, so we cannot
assume they are the same.

After the initial expansion, we group them by name and then create a new
Dependency object for each name, merging the options from each group.

Fixes #20335.
youtube-dl: revert Python 2.x and 3.x support

This makes youtube-dl harder to use as just a script, and people who
need it to call it from python can just install via pip.

This reverts commit e83a9bec485e218dd449df93c5564c834fde1a2a.
riemann 0.2.2

Closes #20353.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
FormulaInstaller: factor out readline workaround
vera++ 1.2.1

Closes #20356.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
git: add note about 1.8.3 being broken
Sniff for non-tarred gzips

Don't try to untar non-tarred gzips.
tesseract: use normal download strategy
graphviz: update --devel version
Ghostscript: add DjVU support

Closes #16830.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
cmake: simplify test slightly
media-info: < 10.6 requires a newer curl

Fixes mistydemeo/tigerbrew#82.
Add :ld64 dependency

This allows formulae which won't build with Tiger's ld to conditionally
request a dependency on the ld64 formula. This modifies the build
environment appropriately, and will only be active on Tiger.
cctools-headers 836
libunwind-headers 35.1
dyld-headers 210.2.3
cctools-headers: Update comment
ld64 97.17