field flags in dbCreate()/dbStruct()

[Antonio Linares]

// 2015-02-08 13:19 UTC+0100 Przemyslaw Czerpak (druzus/at/poczta.onet.pl)
// * src/rdd/workarea.c
// + added support for field flags in dbCreate()/dbStruct().
// Flags can be passed in string with field type after ":", i.e.
// "C:U"
// means Unicode character field.
// The following flags are recognized:
// "N" - column can store null values
// "B" - binary column
// "+" - column is autoincrementing
// "Z" - column is compressed
// "E" - column is encrypted
// "U" - column stores Unicode strings