=========================
You need to install gmp, mpfr, mpc and libiconv packages using MacPorts,
-DarwinPorts or fink. GCC-4.5.1 requires them.
+DarwinPorts or fink. GCC-4.5.1 requires them. You also need wget which can again be obtained from MacPorts etc.
-port install gmp mpfr libmpc
+port install gmp mpfr libmpc wget
For xml support in gdb you may want to install expat too. And add the
--with-expat parameter to GDB target.