Don't use sudo if implicitly called by Pacman frontend

Don't rely on alias expansion to handle Pacman because aliases
are not expanded in sudo.

Signed-off-by: Sorin Ionescu <sorin.ionescu@gmail.com>
Revert "Remove utility aliases for Cygwin"

This reverts commit d368d0536b7e857b8bd98cb7f5f547bac8b96bac.
Revert "Warn that Cygwin is not supported"

This reverts commit b1abe7a84538097bf93e2c6677cedc7d7a980f68.
Merge branch 'master' of https://github.com/sorin-ionescu/prezto