Fix textscan handling of empty fields at end of line (Bug #57612). * oct-stream.cc (skip_whitespace): Change function prototype to have second argument, EOLstop, default to true. * oct-stream.cc (textscan_format_list::read_first_row): Add 2nd argument of false to call to skip_whitespace to reproduce old behavior. * oct-stream.cc (textscan::skip_delim): Delete unnecessary second argument of true to skip_whitespace(). Adjust comments for code. * file-io.cc (Ftextscan): Comment out BIST test for handling of precision which is already incompatibile with Matlab. Add 3 new BIST tests for bug #57612.

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