Build errors with Pyxfce and Xfc from SVN (revision 16828)

[Benedikt Meurer]

Myles Green wrote:
> * Configuring xfc...
> Creating XFC configuration files...
> Building macros...
> Adding libtools...
> Generating makefiles...
> configure.ac: 33: `automake requires `AM_CONFIG_HEADER', not
> `AC_CONFIG_HEADER'
> Generating configure script...

As the message says, there's a typo: The macro is named
AM_CONFIG_HEADER() rather than AC_CONFIG_HEADER(). Fix the typo and
it'll work.

> Best,
> Myles

Benedikt