error() has been removed from Pd's public API...use pd_error( ) instead

with Pd-0.52, the `error()` function has been removed from Pd's public API (the symbol is still exported though for binary compatibility with older externals).

Please update the code to use `pd_error()` instead (which has been around since at least the beginning of Pd's git history (2007), so there shouldn't be any compat issues)