Fix: Placed all +build tags in the same location
Fix: Split CFLAGS, LDFLAGS into seperate lines for readability and lookup
Fix: Placed empty line between copyright comments and build tags for readability
Fix: Placed OS specfic cgo flags at the end if the cgo sections contains multiple lines.
This commit introduces a new type 'ErrNo', implementing the error
interface. Constants for all sqlite3 error codes are provided
in the new source file "error.go".