give load()/include() with target and infile()/$$fromfile() a clean environment

give load()/include() with target and infile()/$$fromfile() a clean environment

load()/include() with a target namespace would inherit the current
context. however, if you source a project with all bells and whistles,
this makes completely no sense and may be actually counterproductive.

infile()/$$fromfile() would have interited only the functions from the
current context. that was only a hack to support abusing them.

Change-Id: I2e992b923d9e5b0e5056001ca49b35de573abc63
Reviewed-by: Joerg Bornemann <joerg.bornemann@nokia.com>