code cleanup (remove "throw string")

pub/src/commands.cpp

pub/src/curve.cpp

pub/src/dualplot.cpp

pub/src/edif.cpp

pub/src/expr.cpp

pub/src/file_in.cpp

pub/src/file_out.cpp

pub/src/list.cpp

pub/src/manip.cpp

pub/src/mem.cpp

pub/src/node.cpp

pub/src/olf.cpp

pub/src/opr.cpp

pub/src/rssm.cpp