vim: upgrade to v7.4.27 and refactor

'vim.inc' is merged into the new recipe 'vim_7.4.27.bb', the recipe is slightly
reorganised and a minor omission in the comments is corrected.

DESCRIPTION is replaced with SUMMARY. PR and INC_PR values are dropped. The
variable PV_MAJOR is also dropped as it isn't used.

LIC_FILES_CHECKSUM is updated as an address and version number given in the
license have been modified. The main license text itself is unchanged.

The setting of PARALLEL_MAKE to force single-threaded compilation is removed as
there is no justification in the git history for this being needed and the
compilation completes fine without it.

Signed-off-by: Paul Barker <paul@paulbarker.me.uk>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>