Don't use build.head? in the DSL
doctor: print values of DYLD_* env vars
Lua >= Lua52

See [this](https://github.com/Homebrew/homebrew/pull/29236) PR for more
details. The previous thread for this PR is
[here](https://github.com/Homebrew/homebrew/pull/31996). I was planning
to rebase but I made a fairly awful mistake mid-rebasing and things
went horribly wrong, so here’s to starting fresh and hopefully not
screwing everything up.
Lua >= Lua52

Yup. I figured it out. When I did the rebasing earlier and messed that
up it pulled out the whitespaces in the _END_ patches, and those spaces
were actually there for a reason and without them… No compile. This
should fix it. Both of these compile locally again.
Lua >= Lua52
Lua >= Lua52

A couple minor changes. Hoping the Ipe change might help a bit. We’ll
see.
gnuplot: update 4.6.5_1 bottle.
highlight: add 3.18_1 bottle.
imapfilter: update 2.5.6_2 bottle.
kyoto-tycoon: add 0.9.56_1 bottle.
libquvi: update 0.4.1_1 bottle.
lighttpd: update 1.4.35_1 bottle.
lsyncd: add 2.1.5_1 bottle.
lua: add 5.2.3_1 bottle.
lua51: update 5.1.5 bottle.
luabind: add 0.9.1_1 bottle.
luarocks: add 2.1.2_1 bottle.
macvim: add 7.4-73_1 bottle.
metalua: add 0.5-rc2_1 bottle.
monotone: update 1.1_1 bottle.