Rename getenv and putenv to getEnv and putEnv, respectively.

We use camel case everywhere else.

Change-Id: I8a67f1d44659d59e612c0eaced0628c6d34d5b47
Reviewed-by: Jake Petroules <jake.petroules@petroules.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>