libfortran: Fix handling of formatted separators.

libfortran: Fix handling of formatted separators.

	Backport from mainline.

	PR libfortran/114304
	PR libfortran/105473

libgfortran/ChangeLog:

	* io/list_read.c (eat_separator): Add logic to handle spaces
	preceding a comma or semicolon such that that a 'null' read
	occurs without error at the end of comma or semicolon
	terminated input lines. Add check and error message for ';'.
	Accept tab as alternative to space.
	(list_formatted_read_scalar): Treat comma as a decimal point
	when specified by the decimal mode on the first item.

gcc/testsuite/ChangeLog:

	* gfortran.dg/pr105473.f90: Modify for revised checks.
	* gfortran.dg/pr114304-2.f90: New test.
	* gfortran.dg/pr114304.f90: New test.