sticker/Database: require SQLite 3.7.3

SQLite 3.7.3 is the version shipped in Debian Squeeze (oldstable);
should be old enough to be the required version.  Drop the
compatibility #ifdef.
sticker/Database: remove redundant sqlite3_reset() calls

Call sqlite3_reset() only after a sqlite3_stmt* has been used, not
before.  Assume it is already in reusable state.
lib/sqlite/Domain: add Domain instance for SQLite

Replaces the sticker_domain for Error::domain.
sticker/Database: move SQLite helpers to lib/sqlite/Util.hxx
sticker/Database: add wrapper for sqlite3_step()
lib/sqlite/Util: add ExecuteModified()
sticker/Database: always invoke sqlite3_reset() and sqlite3_clear_bindings()
sticker/Database: use the Error library
sticker/Database: move code to BindFind()
sticker/Song: add enum StickerOperator to sticker_song_find()
sticker/Match: add operator "EQUALS"

Mapped to "=" in the MPD protocol.  This is the first operator,
initially supporting value matches in the MPD protocol.
sticker/Match: add inequality operators