enchant: add PACKAGECONFIG for *spell

enchant: add PACKAGECONFIG for *spell

* use PACKAGECONFIG for various *spell implementations

* keep aspell enabled by default

* prevent hunspell/myspell being autodetected as reported in "bitbake world status" e-mails:
  WARN: enchant: enchant rdepends on hunspell, but it isn't a build dependency?

(From OE-Core rev: d7df8092c2be4c984d9292749f6cfa7ce41cbb53)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>