Search for the first matching tests directory instead for the last one.
Fix last placeholders test: clear the database before entering NULL
Allow storing and retrieving numerics from string columns and strings from numeric columns.
Merge branch 'version-2' of github.com:Wassasin/librusql into version-2

Conflicts:
	tests/placeholders.cpp
Merge branch 'version-2' of github.com:Wassasin/librusql into version-2