companion-libs: PPL/CLooG/MPC require GMP and MPFR

The PPL, CLoog/ppl and MPC libraries require GMP and MPFR.
Select GMP/MPFR appropriately.

tools wrapper: introduce the silent WRAPPER_NEEDED config option

Add the WRAPPER_NEEDED silent config option, that can be selected by
components that require it (companion libs so far).
Rely on this config option when deciding to install the wrapper,
instead of checking GMP/MPFR or PPL/CLoog/MPC.

Merge the C wrapper.

config: choose whether to use the shell or the C wrapper

Offer a config choice on whether to isntall the script wrapper, or
the compiled C wrapper. Update docs/overview.txt accordingly.

tool wrapper: add initial wrapper coded in C

Add an initial wrapper:
- find the realpath of the tool being called
- add the '.' in front of the tool name
- add the '/lib' dir to the base dir of the tool
- set and export LD_LIBRARY_PATH
- execve the real tool

overview: fix table of content, fix the hacker's way

table of content: add missing entry
the hacker's way: no need to "make install"

README: fix some space alignment

duma: fix downloading by forcing extension to .tar.gz

Downoading a non-existing file from sourceforge gives you a "200 OK"
and an index.html. As we try to retrieve a .tar.bz2 first, and duma
is bundled in a .tar.gz, we won't get appropriate content, so
just force the extension to avoid the problem.

Thanks to Ingmar Schraub <is@eseco.de> for pointing out the issue.

x86_64: is a MMU-aware arch, so select ARCH_USE_MMU

duma: fix version string.

DUMA uses '_' not '.' for major/minor/sub separation.