Howard Chu authored Jan 12, 2014 and Quanah Gibson-Mount committed Jan 13, 2014

free(NULL) is supposed to be safe. "Portable wrapper libraries"
that fail to preserve this behavior are inherently broken.
But then again, this is Mozilla code, so that's redundant.

This reverts commit 75494c08,
which must await a fix to ITS#7771 (DUPSORT cursor tracking).

db_mid2l_insert(): Move assert to mdb.c.
mdb_cursor_set(): Previous assert cannot fail now.
mdb_cursor_put(): Check mc/key and return EINVAL.
mdb_cursor_dbi(): No error return, so just segfault if cursor==NULL.

This should likely be reverted when all callers handle these errors.

mdb_cursor_put(): Use free sub-page space added by a
previous put(existing DUPSORT item), if any.
Tweak NUMKEYS code to avoid a new signedness warning.