title: Can't install summarise gem on OSX, missing glib.h
body: <p>I'm trying to install this gem, <a href="https://github.com/ssoper/summarize" rel="nofollow">summarize</a>, by running:</p>
  
  <pre><code>gem install summarise
  </code></pre>
  
  <p>I get the error:</p>
  
  <pre><code>ERROR: Failed to build gem native extension.
  ...
  In file included from article.c:25:
  ./libots.h:24:10: fatal error: 'glib.h' file not found
  </code></pre>
  
  <p>But when i try and run:</p>
  
  <pre><code>brew install glib
  </code></pre>
  
  <p>i get:</p>
  
  <pre><code>glib-2.38.2 already installed
  </code></pre>
  
  <p>Any ideas on what to try next?</p>
  
  <hr>
  
  <p>EDIT:
  I've since tried:</p>
  
  <pre><code>export CPPFLAGS=-I/usr/local/Cellar/glib/2.38.2/include/glib-2.0/
  export LDFLAGS=-L/usr/local/Cellar/glib/2.38.2/lib/
  export PKG_CONFIG_PATH=/usr/local/Cellar/glib/2.38.2/lib/pkgconfig/
  </code></pre>
  
  <p>...and that seems to have allowed me to move on to a new error:</p>
  
  <pre><code>compiling article.c
  article.c:107:37: warning: passing 'const unsigned char *' to parameter of type 'const char *' converts between pointers to integer types with different sign [-Wpointer-sign]
  if ((aWord == NULL) || (0==strlen(aWord)) ||(NULL==aLine)) return;
                                  ^~~~~
  /usr/include/string.h:82:28: note: passing argument to parameter here
  size_t   strlen(const char *);
                          ^
  article.c:109:68: warning: passing 'const unsigned char *' to parameter of type 'const gchar *' (aka 'const char *') converts between pointers to integer types with different sign [-Wpointer-sign]
  aLine-&gt;words = g_list_append (aLine-&gt;words, (gpointer) g_strdup (aWord));
                                                                 ^~~~~
  /usr/local/Cellar/glib/2.38.2/include/glib-2.0/glib/gstrfuncs.h:216:52: note: passing argument to parameter 'str' here
  gchar*                g_strdup         (const char *str) G_GNUC_MALLOC;
  </code></pre>
  
  <p>...</p>
  
  <pre><code>dictionary.c:28:10: fatal error: 'libxml/xmlmemory.h' file not found
  #include &lt;libxml/xmlmemory.h&gt;
  </code></pre>