Fix interleaving of Fortran STOP messages

Fix interleaving of Fortran STOP messages

Fortran STOP and ERROR STOP use a different function to print the "STOP" string
and the message string.  On GCN this results in out-of-order output, such as
"<msg>ERROR STOP ".

This patch fixes the problem by making estr_write use the proper Fortran write,
not C printf, so both parts are now output the same way.  This also ensures
that both parts are output to STDERR (not that that means anything on GCN).

2018-09-12  Kwok Cheung Yeung  <kcy@codesourcery.com>

	libgfortran/
	* runtime/minimal.c (estr_write): Define in terms of write.

From-SVN: r264239