[complib:mpfr] Fix building MPFR in some weird cases

The tmul test uses a compiled-in input file in $(srcdir).
The problem is that the Makefile passes it unquoted. The C code
tries to stringify it using clever macros, which may *usually* work.

In my case the source directory was named:
.../toolchain-powerpc-e500v2-linux-gnuspe-1.0-2.fc10/.../tests
And guess what? During testing I found out the program fails because
it tries to open:
.../toolchain-powerpc-e500v2-1-gnuspe-1.0-2.fc10/.../tests

Yes, CPP tokenized the macro before stringifying it and not surprisingly
the 'linux' part was converted to 1.
[on Fedora-10: cpp (GCC) 4.3.2 20081105 (Red Hat 4.3.2-7)]

So the attached patch simplify the macros and pass the path as string
from the Makefile.

Manually backported from 1449:8ad2773e7ae3

This is the README for crosstool-NG

To get you started, just enter:

  ./configure --help

You can find a (terse and WIP) documentation in docs/overview.txt.

You can also point your browser to

  http://ymorin.is-a-geek.org/dokuwiki/projects/crosstool

If you need to send a bug report or a patch, please send a mail with subject

prefixed with "[CT_NG]" with the following destinations:

    TO: yann.morin.1998 (at) anciens.enib.fr

    CC: crossgcc (at) sourceware.org

The people that helped are listed in docs/CREDITS. Many thanks to them! :-)

The list of known issues is listed in docs/known-issues.txt.

Aloha!