title: Can't install 'ihaskell-diagrams' using Cabal
body: <p>When I try to </p>
  
  <pre><code>cabal install ihaskell-diagrams
  </code></pre>
  
  <p>I get the error</p>
  
  <blockquote>
    <p>The pkg-config package 'glib-2.0' is required but it could not be
    found.</p>
  </blockquote>
  
  <p>What is <code>glib</code> and how do I install it so that it is available for Cabal?</p>
  
  <hr>
  
  <pre><code>Resolving dependencies...
  Configuring cairo-0.13.1.0...
  Configuring glib-0.13.2.1...
  Failed to install cairo-0.13.1.0
  Build log ( /Users/Rax/.cabal/logs/cairo-0.13.1.0.log ):
  [1 of 2] Compiling SetupWrapper     ( /var/folders/b6/3rk65h797p7407x7d36sqn9c0000gn/T/cabal-tmp-57646/cairo-0.13.1.0/SetupWrapper.hs, /var/folders/b6/3rk65h797p7407x7d36sqn9c0000gn/T/cabal-tmp-57646/cairo-0.13.1.0/dist/setup/SetupWrapper.o )
  [2 of 2] Compiling Main             ( /var/folders/b6/3rk65h797p7407x7d36sqn9c0000gn/T/cabal-tmp-57646/cairo-0.13.1.0/dist/setup/setup.hs, /var/folders/b6/3rk65h797p7407x7d36sqn9c0000gn/T/cabal-tmp-57646/cairo-0.13.1.0/dist/setup/Main.o )
  Linking /var/folders/b6/3rk65h797p7407x7d36sqn9c0000gn/T/cabal-tmp-57646/cairo-0.13.1.0/dist/setup/setup ...
  [1 of 2] Compiling Gtk2HsSetup      ( Gtk2HsSetup.hs, dist/setup-wrapper/Gtk2HsSetup.o )
  [2 of 2] Compiling Main             ( SetupMain.hs, dist/setup-wrapper/Main.o )
  Linking dist/setup-wrapper/setup ...
  Configuring cairo-0.13.1.0...
  setup: The pkg-config package 'cairo' version &gt;=1.2.0 is required but it could
  not be found.
  Failed to install glib-0.13.2.1
  Build log ( /Users/Rax/.cabal/logs/glib-0.13.2.1.log ):
  [1 of 2] Compiling SetupWrapper     ( /var/folders/b6/3rk65h797p7407x7d36sqn9c0000gn/T/cabal-tmp-57647/glib-0.13.2.1/SetupWrapper.hs, /var/folders/b6/3rk65h797p7407x7d36sqn9c0000gn/T/cabal-tmp-57647/glib-0.13.2.1/dist/setup/SetupWrapper.o )
  [2 of 2] Compiling Main             ( /var/folders/b6/3rk65h797p7407x7d36sqn9c0000gn/T/cabal-tmp-57647/glib-0.13.2.1/dist/setup/setup.hs, /var/folders/b6/3rk65h797p7407x7d36sqn9c0000gn/T/cabal-tmp-57647/glib-0.13.2.1/dist/setup/Main.o )
  
  Linking /var/folders/b6/3rk65h797p7407x7d36sqn9c0000gn/T/cabal-tmp-57647/glib-0.13.2.1/dist/setup/setup ...
  [1 of 2] Compiling Gtk2HsSetup      ( Gtk2HsSetup.hs, dist/setup-wrapper/Gtk2HsSetup.o )
  [2 of 2] Compiling Main             ( SetupMain.hs, dist/setup-wrapper/Main.o )
  Linking dist/setup-wrapper/setup ...
  Configuring glib-0.13.2.1...
  setup: The pkg-config package 'glib-2.0' is required but it could not be
  found.
  cabal: Error: some packages failed to install:
  cairo-0.13.1.0 failed during the configure step. The exception was:
  ExitFailure 1
  diagrams-cairo-1.3.0.5 depends on glib-0.13.2.1 which failed to install.
  glib-0.13.2.1 failed during the configure step. The exception was:
  ExitFailure 1
  ihaskell-diagrams-0.3.1.0 depends on glib-0.13.2.1 which failed to install.
  pango-0.13.1.0 depends on glib-0.13.2.1 which failed to install.
  </code></pre>