Make quality improvements

- Write some more unit tests
- memcpy() on ARM is now faster
- Address the Musl complex math FIXME comments
- Some libm funcs like pow() now support setting errno
- Import the latest and greatest math functions from ARM
- Use more accurate atan2f() and log1pf() implementations
- atoi() and atol() will no longer saturate or clobber errno

test/BUILD.mk

@@ -4,7 +4,8 @@
 .PHONY:		o/$(MODE)/test
 o/$(MODE)/test:	o/$(MODE)/test/dsp	\
 		o/$(MODE)/test/libc	\
-		o/$(MODE)/test/net	\
 		o/$(MODE)/test/libcxx	\
+		o/$(MODE)/test/math	\
+		o/$(MODE)/test/net	\
 		o/$(MODE)/test/posix	\
 		o/$(MODE)/test/tool