tracker-extract: Use incremental checksum calc to avoid memory use
tracker-extract: Use incremental checksum calc to avoid memory use

For large files the use of g_file_get_contents wasn't a very good
idea. Instead with this patch we change that to use the support
for incrementally calculating the checksum, and then using a
GFileInputStream to read from the file in chunks of 1024 bytes.

outofbits/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker