Bump NQP_REVISION for fixes to nqp::copy and some CCLASS constants
add symlink and link
run new test file copy.t
let require take paths too

If require`s argument contains a slash or dot treat it like a path
to a file. This means that the file is searched relative to cwd,
variables like CUSTOM_LIBS and INC are not used.
RT #117583: guard against NULL container spec
Convert pir::const::CCLASS_PRINTING to nqp::