use 4.8 toolchain by default

...

 Changes to be committed:
	modified:   core/combo/TARGET_linux-arm.mk
	modified:   core/combo/TARGET_linux-mips.mk
	modified:   core/combo/TARGET_linux-x86.mk
	modified:   core/config.mk
	modified:   core/linaro_compilerchecks.mk

Change-Id: I18af2b50f5e248c24bb910a84ad77aaf63a0f5d5
Merge branch 'rz-4.2-test' of https://github.com/MikereDD/android_build into rz-4.2-test