[ABAP] Fix_column make the scroll horizontally disable~!!

Fix_column is an attribute of alv field.

• Fix_column (fix column): This parameter is used to fix certain columns in the output. All columns to be fixed must have this flag, starting from the left. If a column without this flag is output, only the columns to the left of this column are fixed. The user can change the column fixing interactively.

Value set: SPACE, X.

X = column fixed (does not scroll horizontally).