This is libconfig. Originally from the WAND package found at 
http://wand.sf.net/ or http://www.wlug.org.nz/WanDaemon

Version 1.0.5

INSTALLATION NOTES
==================
Type "make" followed by "make install". This will install libconfig
in /usr/local/lib and place libconfig.h in /usr/local/include. 

LIBCONFIG USAGE
===============

/* Example:
 *
 * #include <stdio.h>
 * #include <libconfig.h>
 *
 * // daemonised is used to tell libconfig if we have backgrounded or not.
 * // libconfig will log to stderr if we haven't, otherwise it will log 
 * // to syslog.
 * 
 * int daemonised = 0;
 * int foo;
 * char *bar;
 *
 * config_t config[] = {
 * 	{ "foo", TYPE_INT|TYPE_NOTNULL, &foo },
 *      { "bar", TYPE_STR|TYPE_NULL, &bar },
 * 	};
 *
 * int main(int argc,char **argv) 
 * {
 *  if(parse_config(config,"/usr/local/etc/wand.conf")) {
 *    return 1;
 *  }
 *
 *  printf("foo=%i\n",foo);
 *  if (bar) {
 *    printf("bar=%s\n",bar);
 *  }
 *  return 0;
 * }
 */