Eclipse/Transit choice

This is for private purposes. Not meant to be used by public.
Took Patricio's commit from March 19th, 2014 and implemented eclipse/transit choice path. Currently committing just changes compared to his commit so he can pull them (take next commit for the full code). Added eclipse.c with all functions needed for eclipse calculation: totaltau_eclipse, tau_eclipse, eclipse_intens, emergent_intens, printecl, eclipsepath. In transit.c path solution variable and if statement for eclipse/transit choice are added. In argum.c new parameter is set, new solutions is defined and read. In Rules.mk eclipse source file is added for compiling. In proto_argum.h new function defined in argum.c is declared. Proto_eclipse.h is made with function defined in eclipse.c. In structure_tr.h eclipse ray solution is made, new parameter is added to transithint structure and transit structures, new type ray solution enum variable is defined. In transit.h eclipse ray solution and proto_eclipse.h are included. In Makefile new PUFLAG is added so the code can compile with 'make transit'.

First Eclipse Implementation

This is for private purposes. Not meant to be used by public.
Do not want to overwrite with Patricio's new version from March 19th 2014, because the base for this eclipse implementation is Pato's Rojo original code from December 19th, 2012, that I know it works "transit-2012-12-19-JB" .