ext: backend: embed timestamp into extension header
ext: leveldb: added extension support
ext: leveldb: parse extensions in range request
ext: eblob: simplified extension stubs
ext: backend: simplifications, comments and leaks
ext: backend: naming cleanups
ext: leveldb: fixed potential leaks
leveldb: w/s nazzi
misc: codespell
leveldb: we have scm - no need to keep commented code

Commented code can be used as documentation or templates, but this was
useless.
leveldb: added __unused (e)glibc note
ext: leveldb: do not free *datap on iteration