Added preprocessor macros which make file and path names of uniform
length

There are three macros #FNAME_LEN, #PNAME_LEN and #PFNAME_LEN,
which are defined in variab.h and variabex.h. These stand for
FileName length, Pathname length and full-pathname length
respectively, and #PFNAME_LEN must be set to the sum of the
first two. Once these have been inserted wherever file and path
names are used, these should help reduce the incidence of segfaults,
buffer-overflows and memory leaks due to mismatched array lengths.
The majority of these have been fixed in variab.h and vinput.c
but there may be more out there to be patched.
Finishing up standardizing file/path name lengths
updated changelog