Marc:
Here are some proposed patches:
misc/install-gnu-gcc-osx: Update gcc to 4.8.2 (4.8.1 has a bug where it won't recognize my Core i7 4770 properly). Send error messages to build.log. Allow parallelism of 8.
lib/_num.scm: Get (expt x y) correct when x is complex, y is an (odd) multiple of 1/2, and the answer is exact. Use ##sqrt for (expt x 1/2) for complex x.
tests/unit-tests/03-number/expt.scm: Add tests for the new functionality, and for a bit of the old functionality.
I just used misc/install-gnu-gcc-osx on my Ubuntu 13.10 box, and it works fine; perhaps it should be renamed to simply misc/install-gnu-gcc.
Brad