Configure test for BG/P fails to identify need for _FILE_OFFSET_BITS.
The configure test on BG will result in the _LARGEFILE64_SOURCE macro being set but not the _FILE_OFFSET_BITS=64 macro. This results in off_t being defined as 32 bits instead of 64. This means the CP_MAX_BYTE_WRITTEN and CP_MAX_BYTE_READ can not be larger than 32 bits.