NAGFOR build with full debug mode

[talassio]

Add support to a new debug build using NAGFOR and all debug features, mainly to build the RALFit package with the flags:

nagfor -g -nan -C=all -C=undefined -u -ieee=full -kind=unique -f2003 -thread_safe -W0,-gline 

Note NAGFOR Fortran compiler has a wide range of debug capabilities, amongst them is the feature to detect referenced but not assigned objects by using the "-C=undefined" switch. This feature produces an "enhanced" signature for each subroutine and objects compiled without it cannot be linked with object compiled with it.