Fixes Homebrew/homebrew#29651.

This fixes external commands that provide their own
help and version subcommands.

Closes Homebrew/homebrew#26755.

I'm not sure why I thought reinventing object instantiation was a good
idea.

We only need one copy of each of these strings, not ~7500.

The default arguments were removed from these methods long ago, so
nothing is standing in the way of using define_method here.

Closes Homebrew/homebrew#28560.

Due to the fragility of the code, this functionality was removed in
recent refactorings of the tap code.

It is possible to restore these features, but it needs to be done in
a cleaner, more maintainable way.

Closes Homebrew/homebrew#29585.

Formula#path can no longer be a symlink.

No Xcode 5.1 support.

Closes Homebrew/homebrew#29488.

As per 9ab605c7f1883 removal of `brew dirty`. `--multiple` *implies*
`--versions`, thus IMO it shouldn't be necessary to also explicitly
include the `--versions` option, but that's a separate matter. For now
this offers the small added convenience of:

    $ brew list --m<TAB><TAB>

to quickly expand the `brew dirty` equivalent.

Closes Homebrew/homebrew#29571.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Closes Homebrew/homebrew#29555.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

Closes Homebrew/homebrew#29476.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

'-fno-tree-pre' and '-fno-tree-dominator-opts'

Closes Homebrew/homebrew#29452.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>