use gnulib:: qualifiers for more stdio functions * oct-parse.yy (text_getc): Use gnulib::getc instead of getc. (looking_at_classdef_keyword, looking_at_funciton_keyword): Use gnulib::ftell, gnulib::fseek, and gnulib::fgets instead of ftell, fseek, and fgets. * file-io.cc (Fmkstemp): Use gnulib::mkstemp instead of mkstemp. * lo-utils.cc (octave_fgets): Use gnulib::fgets instead of fgets. * c-file-ptr-stream.h (c_file_ptr_buf::seek): Use gnulib::fseek instead of fseek. (c_file_ptr_buf::tell): Use gnulib::ftell instead of ftell.