Minor Makefile fixes

[Arjan van de Ven]

Adam Jackson wrote:
> Attached patch from Fedora CVS does two things:
> 
> - 'mkdir -p' on the install directory, for the case where $DESTDIR is an
> empty install root.
> - Set CFLAGS with ?=, not =, so the environment can override it.
> 
> Please apply.
> 
> - ajax
> 
> 
> ------------------------------------------------------------------------
> 
> --- powertop/Makefile.build-fixes	2007-05-13 13:22:08.000000000 -0400
> +++ powertop/Makefile	2007-05-13 21:26:01.000000000 -0400
> @@ -1,13 +1,14 @@
>  BINDIR=/usr/bin
>  
> -WARNFLAGS=-Wall
> -CFLAGS=-O2 -g ${WARNFLAGS}
> +WARNFLAGS = -Wall
> +CFLAGS ?= -O2 -g ${WARNFLAGS}

ok this should solve all the makefile issues brought up
I just committed a final version (I hope)...

can everyone who has been doing makefile fixes check that current SVN 
looks right?