Fortran: error recovery on invalid array section [PR108609]

Fortran: error recovery on invalid array section [PR108609]

The testcase for PR108527 uncovered a latent issue with invalid array
sections that resulted in different paths being taken on different
architectures.  Detect the invalid array declaration for a clean recovery.

gcc/fortran/ChangeLog:

	PR fortran/108609
	* expr.cc (find_array_section): Add check to prevent interpreting an
	mpz non-integer constant as an integer.

gcc/testsuite/ChangeLog:

	PR fortran/108609
	* gfortran.dg/pr108527.f90: Adjust test pattern.