Treat sqlite3.c amalgamations as a "package" and/or a generated file

[pombredanne]

These are very large C file with this typical header:

/******************************************************************************
** This file is an amalgamation of many separate C source files from SQLite
** version 3.8.7.2.  By combining all the individual C code files into this 
** single large file, the entire code can be compiled as a single translation
** unit.  This allows many compilers to do optimizations that would not be
** possible if the files were compiled separately.  Performance improvements
** of 5% or more are commonly seen when SQLite is compiled as a single
** translation unit.