Add verbosity flag to determine whether library prints to stdout

[edwardhartnett]

Currently the library prints error messages. For example from getidx():

  else
     nlen = 0
     nnum = 0
     print *, ' '
     print *, ' error reading index file '
     print *, ' '
     iret = 96
     return

Libraries should not print anything. The calling application is in charge of stdout and can decide whether or not to print anything. The library simply should return an error code.

So we need a setting for verbosity. If it's turned off, no messages are ever printed to stdout.

Not sure how to handle this global setting...