Fix cmake script for searching sqlite3 properly.

This is important for Debian, Ubuntu and other systems based on them. Details:
  https://wiki.debian.org/Multiarch
  https://wiki.ubuntu.com/MultiarchSpec

Have in mind that there are MIPS, ARM and many other architectures...
Merge pull request #20 from tehnick/cmake-sqlite3-fix

Fix cmake script for searching sqlite3 properly.