Fix a Number/BigInt descrepancy in oo1.DB() when passed a WASM-string db filename. Consolidate some duplicated internal code and adjacent minor cleanups. (tags: wasm-64bit)

Fix a Number/BigInt descrepancy in oo1.DB() when passed a WASM-string db filename. Consolidate some duplicated internal code and adjacent minor cleanups. (tags: wasm-64bit)