Redmine #6214: Fix memory alignment errors when using LMDB/NextDB().

This was causing SPARC architecture to crash when expecting a struct
in the value, since the struct would be aligned to a byte position
which depended on the length of the key. x86 is also slower when
accessing unaligned data types, so should be an improvement there as
well.
Merge pull request #1788 from kacfengine/sparc_memory_alignment

Redmine #6214: Fix memory alignment errors when using LMDB/NextDB().