load order issue in the error handling code

[attila-lendvai]

cuda-report-errors and cuda-scan-error-buffer are defined in the same file, but the former calls the latter, which can lead to errors if they are called at load time (see #9 where/why that happens).

another toplevel form in that same file tries to initialize the device, which leads to a cuda-invoke, which then leads to a call to cuda-scan-error-buffer which is not yet loaded/defined at that point.

backtrace is available in Xach's report in #8 (the backtrace is not very useful).