Avoid using SQLITE_OPEN_URI

Centos6 uses a very old version of SQLite without support for URI filenames.
PAM authenticator must use a file-based database.

Commit cherry-picked to 2.4.0 from 2.3.

server/modules/authenticator/PAM/PAMAuth/pam_auth.cc

@@ -29,6 +29,9 @@ const string FIELD_AUTHSTR = "authentication_string";
 const string FIELD_PROXY = "proxy_grant";
 const int NUM_FIELDS = 6;
 
+const char* SQLITE_OPEN_FAIL = "Failed to open SQLite3 handle for file '%s': '%s'";
+const char* SQLITE_OPEN_OOM = "Failed to allocate memory for SQLite3 handle for file '%s'.";
+
 /**
  * Initialize PAM authenticator
  *