doc: add generated files: qt-assistant.dcf, qt-assistant.adp, CHMFiles/*.html.

Pro: will reduce the amount of manual configuration users have to perform when packaging GCC4TI before building it;
Con: will pollute diffs...
scripts: make updatesrc copy documentation that was hopefully generated by updatedoc and committed to the repository.
scripts: make updatesrc create a source tree suitable for running scripts/Install from the source tree folder without further user action; update README and INSTALL.
scripts: add and document the possibility to skip recompilation of binutils and gcc, thereby speeding up the recompilation process for power users.
ld-tigcc: replace several non-standard nested functions by standard static inline functions or macros.
scripts: in launch.gcc, fail the build if moving cc1 failed.
gcc4tidoc: look for "assistant", "assistant-qt3" and "assistant_adp", not just "assistant".
a68k: when recognizing a register definition, handle "fp" as well. Patch by Martial "Folco" Demolins.
includes: don't #include <default.h> from a number of headers which don't depend on anything from that header.
scripts: add a symlink to $PREFIX_GCC4TI/doc/html/index.html in $PREFIX_GCC4TI/doc. Suggested by Martial "Folco" Demolins.
gcc4tidoc: look for "assistant_adp" and "assistant-qt3" before looking for "assistant".