cairo: don't allow opting-out of glib dep

Lots of stuff in Homebrew needs this, probably more than we are aware
of, and the vast majority of people installing cairo will have glib
anyway.
Use symbol form of freetype dep where appropriate
Use accessors to silence uninitalized ivar warnings
keg_only_reason and cc_failures are not DSL methods
Silence more warnings
Extract constants for checkums in tests
pdf2svg: fix poppler dep
versions: delete unused method
bottle: clean up after interrupts
bottle: re-raise interrupt after cleanup
Implement hash equality for Version
versions: restore original constant

Before:

  f1 = Formula.factory('tree')
  f1.versions
  f2 = Formula.factory('tree')
  f1.class == f2.class # => false

After:

  f1 = Formula.factory('tree')
  f1.versions
  f2 = Formula.factory('tree')
  f1.class == f2.class # => true
discount 2.1.7
fuzzy-find 0.6.0

Closes #25091.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
dart 30798

Closes #25089.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
datomic 0.9.4331

Closes #25082.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
jbossforge 1.4.3.Final

Closes #25088.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
nexus 2.7.0-04

Closes #25094.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
selenium-server-standalone 2.38.0

Closes #25096.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
sbuild 0.7.0

Closes #25075.

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