This patch fixes the regression by increasing the limit where we fall
back to runtime to 2**28 elements, which is the same limit where
previous releases failed. The are still bugs in the runtime
evaluation, so in many cases longer characters will still fail, so
print a warning message.

Regtested on x86_64-pc-linux-gnu.

gcc/fortran/ChangeLog:

2018-02-01  Janne Blomqvist  <jb@gcc.gnu.org>

	PR fortran/83705
	* simplify.c (gfc_simplify_repeat): Increase limit for deferring
	to runtime, print a warning message.

gcc/testsuite/ChangeLog:

2018-02-01  Janne Blomqvist  <jb@gcc.gnu.org>

	PR fortran/83705
	* gfortran.dg/repeat_7.f90: Catch warning message.

From-SVN: r257281