example_starts_with prints logical results as binary

[sscalpone]

This line of code

  print'(a)', starts_with("pattern", "pat")  ! T

in stdlib/example/strings/example_starts_with.f90
prints binary because of the a format.

It's not a problem per se, but just checking if it's intentional.

% gfortran example_starts_with.f90
% a.out |& cat -v
^A^@^@^@
^@^@^@^@
%