Add the WITH_P4IMPORT knob to the Makefile.
Add the WITH_P4IMPORT knob to the Makefile.

WITH_P4IMPORT: enables the installation of the Perforce import
script.

Signed-off-by: Eygene Ryabinkin <d584d646d1a2b0c04e665c4dd5632c4a4e24f130@codelabs.ru>
Signed-off-by: Junio C Hamano <dc50d1021234060e53ec42a77d526afa2fe07479@cox.net>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git