title: How to fix my brew doctor errors?
body: <p>Running brew doctor on my mountain lion terminal , I get the following errors :</p>
  
  <pre>
  <code>
  <strong>Warning</strong>: /usr/local/etc isn't writable.
  This can happen if you "sudo make install" software that isn't managed
  by Homebrew.
  
  If a brew tries to write a file to this directory, the install will
  fail during the link step.
  
  You should probably `chown` /usr/local/etc
  Warning: Some directories in /usr/local/share/man aren't writable.
  This can happen if you "sudo make install" software that isn't managed
  by Homebrew. If a brew tries to add locale information to one of these
  directories, then the install will fail during the link step.
  You should probably `chown` them:
  
      /usr/local/share/man/man8
  <strike><strong>Warning</strong>: Your XQuartz (2.7.2) is outdated
  Please install XQuartz 2.7.4.</strike>
  <strong>Warning</strong>: Unbrewed dylibs were found in /usr/local/lib.
  If you didn't put them there on purpose they could cause problems when
  building Homebrew formulae, and may need to be deleted.
  
  Unexpected dylibs:
      /usr/local/lib/libicudata.49.1.2.dylib    /usr/local/lib/libicui18n.49.1.2.dylib    /usr/local/lib/libicuio.49.1.2.dylib    /usr/local/lib/libicule.49.1.2.dylib    /usr/local/lib/libiculx.49.1.2.dylib    /usr/local/lib/libicutest.49.1.2.dylib    /usr/local/lib/libicutu.49.1.2.dylib    /usr/local/lib/libicuuc.49.1.2.dylib
  <strong>Warning</strong>: Unbrewed .pc files were found in /usr/local/lib/pkgconfig.
  If you didn't put them there on purpose they could cause problems when
  building Homebrew formulae, and may need to be deleted.
  
  Unexpected .pc files:
      /usr/local/lib/pkgconfig/icu-i18n.pc    /usr/local/lib/pkgconfig/icu-io.pc    /usr/local/lib/pkgconfig/icu-le.pc    /usr/local/lib/pkgconfig/icu-lx.pc    /usr/local/lib/pkgconfig/icu-uc.pc
  <strong>Warning</strong>: Unbrewed static libraries were found in /usr/local/lib.
  If you didn't put them there on purpose they could cause problems when
  building Homebrew formulae, and may need to be deleted.
  
  Unexpected static libraries:
      /usr/local/lib/libc-client.a
  <strong>Warning</strong>: Homebrew's sbin was not found in your path.
  Consider amending your PATH variable so it contains:
    /usr/local/sbin
  </code>
  </pre>
  
  <p>How can I fix these errors?
  Is it critical to fix them or I may ignore them?
  Thank you.</p>