hashvalue was printing garbage in mlog because we advanced the
pointer while computing the hash.   save init value of the pointer
so we don't mlog garbage.
mlog the fd so we know which branch of getattr is run
revise that debug mlog
update some mlogs
add mlog check
add some more mlogs
lost code that handled the case of attempting to merge a zero length
index dropping file.   zero length index dropping files can happen
after a ftruncate() to zero.

in this case we don't want to call GetDataBuf() since that fails
if len == 0.   instead, we just set the buffer to null (and the
0 length will drop us through to the end --- because merging a
zero length dropping is a no-op).
handle the case where we have a zero length global index (unlikely).
add missing code to init pconf->mlog_setmasks.   this was causing
the fuse --mlog_setmasks flag to not work.
BRI wasn't merging write index records that were next to each other.
restore code to do that.
mlog # of entires after merge
add some mlogs for query API
make sure the query resolver fills out all the fields of the index_record
so we don't get unexpected results (e.g. when we are in a hole).
add some mlog for taskgen
set query limit to "<", not "<=" -- wasn't causing a problem
but didn't do what was expected.
spruce up an mlog
to be safe, check for any remaining open data droppings when doing a final
close of a Plfs_fd.   close any found.

XXX: currently this can happen with PLFS/FUSE if a process
opens a file and then forks off a child to do the write.
 the forked proc doesn't generate an open, but it gets sent
to plfs_write() and makes a dropping.  e.g.

	# (eval "gcc -v >&1") 2>conftest.err

even if we fix this (e.g. to have writes use the pid of the opener
rather than the writer), we should keep this code anyway just to
play it safe (doesn't cost much to check).
put in some commented out code in plfs_write() that detects writes
from an unknown pid (i.e. one that hasn't previously talked to us
with an open).   at some point we may want to reject these calls?
(currently getting them from FUSE: (eval "gcc -v >&1") 2>conftest.err
add a comment about pids to f_write().