Allow configuration of gcc version used for build

You can override the default version by setting the value of
TARGET_GCC_VERSION in the BoardConfig.mk file. For example,
to select version 4.6, add the following:

TARGET_GCC_VERSION := 4.6

Change-Id: I10afb47b18c45e2b913b8af8f34cb98e5e96cbf2

Conflicts:
	core/config.mk
Make gcc 4.6 default and non O3

* to use gcc 4.7 add TARGET_GCC_VERSION := 4.7 to your board config
* to use O3 add TARGET_USE_O3

Change-Id: Ia4a00023c84cc21122bdf1c116e51a179ccabd8c
Add optimization paramater to lunch

When you run lunch you can see the optimizations enabled in your boradconfig.mk
Current options are TARGET_GCC_VERSION/TARGET_USE_O3/TARGET_USE_LINARO_STRING_ROUTINES

Change-Id: Ie2870165906129381fdc0c28fc13f26fbb11c22d
Graphite optimizatoin flags

Enable with use TARGET_USE_GRAPHITE
*currently expermental

Change-Id: I2126a86986c4f7eed7252ed40d860b2f74725afb