Minor bug in ./configure

[Dave Peticolas]

Eric Hanchrow writes:
> >>>>> "Eric" == Eric Hanchrow <offby1@blarg.net> writes:
> 
> The problem was that I didn't have libgdk-pixbuf, and `./configure'
> incorrectly reported that problem by saying that it couldn't find
> gtkhtml.  So:
> 
> * there is a bug in configure -- when libgdk-pixbuf is missing, it
>   should say so, but instead it says it cannot find gtkhtml
> 
> And:
> 
> * The README should mention that libgdk-pixbuf is required to build
>   GnuCash.

I have added a check for gdk-pixbuf and updated the README.

thanks,
dave