[gzip_all] Modify test.sh to loop over both SIZES and NFILES, and other fixes/updates.
[gzip_all] Add DYNAMIC_BUFLEN in gzip.c and x variable selection in post_process.sh.
[gzip_all] Fixes for dynamic BUFLEN, cleaner test script, and addition of 4 test cases.
[gzip_all] Add CASE variable to test.sh and post_process.sh.