Meta-commands (commands starting with a \) other than \r are
currently ignored by gp2c, though a warning will be issued, because it
is not clear what they should do in a compiled program. Instead you probably
want to run the meta-command in the GP session itself.
The meta-command \rinclude is replaced with the content of the
file include (or include.gp) when gp2c read the file.
If you would prefer gp2c to link include.so to the program instead,
see Section 2.4.