lib/calib_yacc.y: Move comedi_parse_calibration_file()

lib/calib_yacc.y: Move comedi_parse_calibration_file()

Move the comedi_parse_calibration_file() function definition to the
bottom of the file.  It calls calib_yyparse() and the declaration might
not be in scope since we removed the declaration from
"lib/libinternal.h", but we know it will be declared somewhere above the
bottom of the generated "lib/calib_yacc.c" above the new location of
comedi_parse_calibration_file().