[Proj] Distance calculations

[Irwin Scollar]

The Zhang Xue-Lian method of distance calculation was implemented in 
C in the NIMA/MUSE DTCC4 program for the forward and inverse cases as 
distazm.h and distazm.c.  I converted the inverse implementation to 
Pascal for use in a dll which is freely available

The DTCC4 suite and the web links are no longer available. If anyone 
needs help with this, please ask off-line.

Irwin Scollar