Global locator2longlat (double *longitude, double *latitude, const char *locator)

The fifth pair ranges from aa to xx, there is another convention that ranges from aa to yy. At some point both conventions should be supported.

Global longlat2locator (double longitude, double latitude, char *locator, int pair_count)

locator is not tested for overflow.

The fifth pair ranges from aa to yy, there is another convention that ranges from aa to xx. At some point both conventions should be supported.