title: mysql.h is missing .... (Ruby on Rails, OSX)
body: <p>I tried several ideas ... none of them worked ...
  I'm just trying to install mysql2 as a gem. My mysql is working, but every time  my system says, that mysql.h is missing ... Has someone an idea? It's very frustrating now ...</p>
  
  <p>I'm using osx 10.8.3, ruby 1.9.3, rails 3.2.13 and home-brew.</p>
  
  <pre><code>    gem install mysql2 -v '0.3.11'
  Building native extensions.  This could take a while...
  ERROR:  Error installing mysql2:
      ERROR: Failed to build gem native extension.
  
          /Users/gadreel/.rvm/rubies/ruby-1.9.3-p429/bin/ruby extconf.rb
  checking for rb_thread_blocking_region()... yes
  checking for rb_wait_for_single_fd()... yes
  checking for mysql.h... no
  checking for mysql/mysql.h... no
  -----
  mysql.h is missing.  please check your installation of mysql and try again.
  -----
  *** extconf.rb failed ***
  Could not create Makefile due to some reason, probably lack of
  necessary libraries and/or headers.  Check the mkmf.log file for more
  details.  You may need configuration options.
  
  Provided configuration options:
      --with-opt-dir
      --with-opt-include
      --without-opt-include=${opt-dir}/include
      --with-opt-lib
      --without-opt-lib=${opt-dir}/lib
      --with-make-prog
      --without-make-prog
      --srcdir=.
      --curdir
      --ruby=/Users/gadreel/.rvm/rubies/ruby-1.9.3-p429/bin/ruby
      --with-mysql-config
      --without-mysql-config
  
      file `which mysql`
      /usr/local/mysql/bin/mysql: Mach-O 64-bit executable x86_64
  </code></pre>