[U-Boot] Handling of environment settings

[Alex Dubov]

Until now, custom environment settings were just defined in the board config
file. All that had to be done is to edit the file, recompile the u-boot and
flash it to the target.

Now, however, this approach is not longer acceptable. This means, that
environment must be either set manually on the target or maintained
and flashed as a separate blob, which is considerably less convenient.

So, two question here:
1. Is there a tool already which takes an environment description in some
form and produces a flashable blob?
2. If not, is there some extra include file which is considered
volatile and can hold user-defined environment settings?