The new plugin path API uses char** to represent
a variable lenght vector of variable length strings.
FORTRAN is not capable of accessing such structures.
So, this PR extends the API to provide a counted string-based
API to the plugin path functionality.
The new functions are inserted in the netcdf_aux.h/daux.c files.
The new functions are just wrappers around other plugin path API
function; they are just (I hope) more convenient for FORTRAN users.
The new functions are as follows:
### *ncaux_plugin_path_stringlen(void)*
* Return the length (as in strlen) of the current plugin path directories encoded as a string. Return -1 if the request fails.
### *int ncaux_plugin_path_stringget(int pathlen, char* path)*
* Get the current sequence of directories in the internal global plugin path list encoded as a string path using ';' as a path separator. As an example, it might return "/a/b/c;/home/user/me;/tmp". The arguments are as follows:
* *pathlen* -- the length of the path argument.
* *path* -- a string into which the current plugin path as a string is stored.
* Return NC_NOERR | NC_EINVAL
### *int ncaux_plugin_path_stringset(int pathlen, const char* path)*
* Set the current sequence of directories in the internal global plugin path list. As an example, it might take "/a/b/c;/home/user/me;/tmp". The arguments are as follows:
* *pathlen* -- the length of the path argument.
* *path* -- a string that is parsed to obtain the sequence of directories for the current plugin path.
* Return NC_NOERR | NC_EINVAL
