Added GMP and MPFR workaround for EABI GCC. Reorganized the structure to remove duplicated code and collect target specific data in one place. Now installs all compilers to /usr/local/bin, removing the need to point out each compiler separately in PATH. FS#11357
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@26600 a1c6a512-1295-4272-9138-f99709370657