Revert "Add backuptool support to the releasetools system"

This reverts commit 2c4e0420fd78b25156aef8b6db78567f6dde070e.

Conflicts:

	core/Makefile

Change-Id: Ia0c3fea3f7c114b0179acfb572e258ebd6de24c9
Revert "Revert "Add backuptool support to the releasetools system""

This reverts commit 1017eb1f97514a7438b114d2692928081010b635.
envsetup: Set CUSTOM_BUILD environment variable

This is used to gate a few features, including backuptool

Change-Id: I02fee9e0765cca88c833bb0514762aa3b14642e3
recovery: fix custom recoveries

This is a squashed set of commits with some updates to minimize conflict with AOSP

recovery: custom recovery build fixes

Patch by Koush

Extract uboot image creation from core/Makefile

http://memegenerator.net/instance/12495768

This change utilizes BOARD_CUSTOM_BOOTIMG_MK to extract out the Uboot boot and
recovery image generation out into it's own file (approx 130 lines).

This should:
    * Clean up the already huge Makefile and the keep ifdeffyness down
    * Make sure Uboot changes don't effect other builds
    * Extract a lot of code that is only for 3 devices

This depreciates BOARD_USES_UBOOT but BOARD_USES_UBOOT_MULTIIMAGE is still valid.

Boards who use uboot boot images should remove BOARD_USES_UBOOT and add
  BOARD_CUSTOM_BOOTIMG_MK := device/common/uboot-bootimg.mk
to their BoardConfig.mk
(location of the makefile is not finalized)

Conflicts:
	core/Makefile

Patch by nemith

remove unused BOARD_USES_COMBINED_RECOVERY

Change-Id: I79520c510488d63d469b0d1a3a099420f7de1fe6

Patch by codeworkx

Change-Id: I6bcab88b76272526bdc558fbf8d7b43347bb5ef1
core: Support GNU make 4.0 and any future releases

http://lists.gnu.org/archive/html/make-w32/2013-10/msg00021.html

Change-Id: Iaf6aa32e64269bf0368c20b0393e3fcfa540558d