OK, magic is completely resolved:
- on 64-bit compile everything is OK because of 64-bit size_t
- on unix 32 bit compile all is OK because fseek's offset is long, so 32 bit
- on 32-bit LibRaw with file interface, LibRaw_file_datastream is used by default. It is based on 32-bit std::streambuf, so out-of-range offset is converted back to 32-bit '-53' (for the sample).

So, only bigfile_datastream (not used for small files by default) and buffer_datastream (read from memory) are affected.

Fortunately, this is the only place where strlen is used as fseek() parameter.

BTW, best way to fix looks like (in the beginning of dcraw_common.cpp):

int my_strlen(const char *str)
{
	return (int)strnlen(str,0x7fffffff);
}
#define strlen(a) my_strlen((a))