scripts: allow logging of commands with variables

In a lot of places, we need to call some commands with specific
variable settings, a-la:
var1=val1 var2=val2 /foo/bar/buz opt1 opt2

Unfortunately, we currently can not log the variable settings.

Enhance CT_DoExecLog with a crude heuristic that works pretty well
and that can also log setting variables.

Reported-by: ANDY KENNEDY <ANDY.KENNEDY@adtran.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

This is NOT the official version of dialog.  This version has been

significantly modified from the original.  It is for use by the Linux

kernel configuration script.  Please do not bother Savio Lam with 

questions about this program.