ext: stubs
misc: notes and whitespaces
ext: removed code duplication
ext: no need for explicit cast
ext: added write-path stubs
Merge branch 'master' into extensions

Conflicts:
	example/eblob_backend.c
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
Merge remote-tracking branch 'upstream/master' into extensions

Conflicts:
	example/leveldb_backend.c
ext: leveldb: fixed leak in write_path