message: generalize the types of std exceptions taken at the API level
diff: @@ -71,7 +71,7 @@ inline std::string toString(OSPObject obj)
  } catch (const std::bad_alloc &) { \
  handleError(OSP_OUT_OF_MEMORY, "OSPRay was unable to allocate memory"); \
  return a; \
  - } catch (const std::runtime_error &e) { \
  + } catch (const std::exception &e) { \
  handleError(OSP_UNKNOWN_ERROR, e.what()); \
  return a; \
  } catch (...) { \
  