Closes Homebrew/homebrew#35142.

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

This deprecates URLs that begin with the following fake URL schemes:
  bzr://
  cvs://
  hg://
  fossil://
  svn+http://

Despite their appearance, they are not actually accepted by the
corresponding tools. They exist only as hints to the download strategy
detection code, and are stripped from the URL before the URL is handed
off to the VCS program.

This is not documented, and may lead one to believe it is a valid URL
that can be used elsewhere, when it actually only works inside Homebrew.

We have a better mechanism for specifying the download strategy that is
straightforward and explicit:
  :using => :hg

Recommend that instead.

Closes Homebrew/homebrew#35114.

Closes Homebrew/homebrew#35080.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

@gapple has taken the mantle of brew services: https://github.com/Homebrew/homebrew/issues/28657#issuecomment-58318215



Closes Homebrew/homebrew#35090.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

This reverts commit f4fe50a0958b7b47b32041e11d4943d6ae7d3972.

See https://gcc.gnu.org/onlinedocs/gcc/Environment-Variables.html

Closes Homebrew/homebrew-versions#592.

Closes Homebrew/homebrew#35027.

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

Some minor changes to reflect Homebrew/homebrew#34989, and other bits and pieces.

Closes Homebrew/homebrew#35023.

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

This reverts commit 028ee18b851497f8aede55004bcdcc5c16f087cc.

Fixes Homebrew/homebrew#32304.
Fixes Homebrew/homebrew#34933.

Closes Homebrew/homebrew#34953.

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

It is called with an explicit receiver in build.rb, so the base class
method should also be public.

native pkg-config support for zlib and sqlite to elimate the need
to pass flags to configure or make stages in formulae.

Closes Homebrew/homebrew#34765.

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

prepend_path doesn't do anything if path doesn't already exist, so use
prepend_create_path.

Closes Homebrew/homebrew#34793.