pkg-autotools: move common macros

Currently, the common macros used for the various hooks are defined for
each and every autotools packages, even though the macros are completely
generic.

Besides being completely useless, it tends to slow down make, as the
variables are redefined over and over again.

Move their definitions out of inner-autotools-package.

Note: we remove the double-$ because we no longer are in a
define-in-a-define block, just a define block.

[Thomas: change back the author to Johan. Yann mistakenly changed it
when submitting the patch series.]

Signed-off-by: Johan Oudinet <johan.oudinet@gmail.com>
[yann.morin.1998@free.fr: split the patch into semantically separate
patches]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Arnout Vandecappelle <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>