Initial install-time test for PCRE compiled without Unicode properties, which causes corruption in feeds and other linking problems.

Error message links to help info at http://status.net/wiki/Red_Hat_Enterprise_Linux#PCRE_library

install.php

@@ -301,6 +301,19 @@ function checkPrereqs()
         $pass = false;
     }
 
+    // Look for known library bugs
+    $str = "abcdefghijklmnopqrstuvwxyz";
+    $replaced = preg_replace('/[\p{Cc}\p{Cs}]/u', '*', $str);
+    if ($str != $replaced) {
+        printf('<p class="error">PHP is linked to a version of the PCRE library ' .
+               'that does not support Unicode properties. ' .
+               'If you are running Red Hat Enterprise Linux / ' .
+               'CentOS 5.3 or earlier, see <a href="' .
+               'http://status.net/wiki/Red_Hat_Enterprise_Linux#PCRE_library' .
+               '">our documentation page</a> on fixing this.</p>');
+        $pass = false;
+    }
+
     $reqs = array('gd', 'curl',
                   'xmlwriter', 'mbstring', 'xml', 'dom', 'simplexml');