Adding an example-formula.rb to show all features

A huge cheat sheet. Kind of.
man brew: Mention the example-formula.rb
brew create: Mention the example-formula
gettext 0.18.3.1
openssl: remove redundant comment
openssl: avoid miscompilations under stdenv with clang and -O3
Avoid the need to compact the expanded deps array
Use ENV.update to restore removed variables