Fortran: Accept again tab as alternative to space as separator [PR114304]

This fixes a side-effect of/regression caused by r14-9822-g93adf88cc6744a,
which was for the same PR.

	PR libfortran/114304

libgfortran/ChangeLog:

	* io/list_read.c (eat_separator): Accept tab as alternative to space.

gcc/testsuite/ChangeLog:

	* gfortran.dg/pr114304-2.f90: New test.

 gcc/testsuite/gfortran.dg/pr114304-2.f90 | 82 ++++++++++++++++++++++++++++++++
 libgfortran/io/list_read.c               |  2 +-
 2 files changed, 83 insertions(+), 1 deletion(-)

diff --git a/gcc/testsuite/gfortran.dg/pr114304-2.f90 b/gcc/testsuite/gfortran.dg/pr114304-2.f90
new file mode 100644
index 00000000000..5ef5874f528
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr114304-2.f90
@@ -0,0 +1,82 @@
+! { dg-do run }
+!
+! PR fortran/114304
+!
+! Ensure that '\t' (tab) is supported as separator in list-directed input
+! While not really standard conform, this is widely used in user input and
+! widely supported.
+!
+
+use iso_c_binding
+implicit none
+character(len=*,kind=c_char), parameter :: tab = C_HORIZONTAL_TAB
+
+! Accept '<tab>' as variant to ' ' as separator
+! Check that <carriage_return><new line> and <new_line> are handled
+
+character(len=*,kind=c_char), parameter :: nml_str &
+   = '&inparm'//C_CARRIAGE_RETURN // C_NEW_LINE // &
+     'first'//tab//'='//tab//' .true.'// C_NEW_LINE // &
+     ' , other'//tab//' ='//tab//'3'//tab//', 2'//tab//'/'
+
+! Check that <carriage_return> is handled,
+
+! Note: For new line, Unix uses \n, Windows \r\n but old Apple systems used '\r'
+!
+! Gfortran does not seem to support all \r, but the following is supported
+! since ages, ! which seems to be a gfortran extension as ifort and flang don't like it.
+
+character(len=*,kind=c_char), parameter :: nml_str2 &
+   = '&inparm'//C_CARRIAGE_RETURN // C_NEW_LINE // &
+     'first'//C_NEW_LINE//'='//tab//' .true.'// C_CARRIAGE_RETURN // &
+     ' , other'//tab//' ='//tab//'3'//tab//', 2'//tab//'/'
+
+character(len=*,kind=c_char), parameter :: str &
+   = tab//'1'//tab//'2,'//tab//'3'//tab//',4'//tab//','//tab//'5'//tab//'/'
+character(len=*,kind=c_char), parameter :: str2 &
+   = tab//'1'//tab//'2;'//tab//'3'//tab//';4'//tab//';'//tab//'5'//tab//'/'
+logical :: first
+integer :: other(4)
+integer :: ints(6)
+namelist /inparm/ first , other
+
+other = 1
+
+open(99, file="test.inp")
+write(99, '(a)') nml_str
+rewind(99)
+read(99,nml=inparm)
+close(99, status="delete")
+
+if (.not.first .or. any (other /= [3,2,1,1])) stop 1
+
+other = 9
+
+open(99, file="test.inp")
+write(99, '(a)') nml_str2
+rewind(99)
+read(99,nml=inparm)
+close(99, status="delete")
+
+if (.not.first .or. any (other /= [3,2,9,9])) stop 2
+
+ints = 66
+
+open(99, file="test.inp", decimal='point')
+write(99, '(a)') str
+rewind(99)
+read(99,*) ints
+close(99, status="delete")
+
+if (any (ints /= [1,2,3,4,5,66])) stop 3
+
+ints = 77 
+
+open(99, file="test.inp", decimal='comma')
+write(99, '(a)') str2
+rewind(99)
+read(99,*) ints
+close(99, status="delete")
+
+if (any (ints /= [1,2,3,4,5,77])) stop 4
+end
diff --git a/libgfortran/io/list_read.c b/libgfortran/io/list_read.c
index b56f2a4e6d6..5bbbef26c26 100644
--- a/libgfortran/io/list_read.c
+++ b/libgfortran/io/list_read.c
@@ -463,7 +463,7 @@ eat_separator (st_parameter_dt *dtp)
 
   dtp->u.p.comma_flag = 0;
   c = next_char (dtp);
-  if (c == ' ')
+  if (c == ' ' || c == '\t')
     {
       eat_spaces (dtp);
       c = next_char (dtp);