Fixes for compatibility with Arch Linux.

Hi Ico, here are my changes to make the build from HEAD go through on Arch (it still works ok on Ubuntu 12.04 as well). Here's a discussion of the issues fixed with this changeset:

- Some Makefiles and scripts require the 'arch' utility which for some reason doesn't exist on Arch, go figure. ;-) I replaced it with the equivalent 'uname -m'.

- flite refuses to configure and build because of linker errors. I added the required libraries in flite/configure.ac. (You still have to run autoconf there so that the changes are picked up and the configure script is updated accordingly.)

- cwiid refuses to build because the default 'python' on Arch is Python 3.3, and the Python stuff in cwiid won't compile with that Python version. I also fixed up the CFLAGS and LDLIBS options using pkg-config so that the right include files and libraries get picked up.

- Arch has Tcl/Tk 8.6 which lacks the default.h and tkUnixDefault.h header files. I simply copied the ones from Tk 8.5 in Ubuntu 12.04 and included them in the tkpath/generic directory.