[oe] chromium 40, gcc 5.3, and OE master problems

[Carlos Rafael Giani]

Recently I did a build of chromium 40 with the current OE-core & meta-oe 
master, which means it was built with GCC 5.3.
Chromium was always crashing, the origin of the segmentation fault was 
somewhere deep inside the GCC std::map implementation.
I added GCCVERSION = "4.9%" to local.conf, rebuilt the image, and 
chromium worked.

Did anybody else observe the same? I built it for the nitrogen6x 
platform (imx6 SoC). I did not yet try it in QEMU.

Also, I have factored code out of the chromium .bb file into a 
chromium-browser.inc file. This way, the existing chromium.inc remains 
usable for cef3, and Chromium upgrades become easier.
(I will upgrade Chromium in a followup commit.)
Since the GCC issue is clearly something separate, I do not think this 
recipe cleanup should be blocked by it. So I will soon post the recipe 
upgrade here, and the GCC issue should be discussed in parallel.