Move math headers in with the other headers.

Keeping them separate is a pain for the NDK, and doesn't help the platform.

Change-Id: I96b8beef307d4a956e9c0a899ad9315adc502582
diff --git a/tests/complex_test.cpp b/tests/complex_test.cpp
index 710912a..3b8e682 100644
--- a/tests/complex_test.cpp
+++ b/tests/complex_test.cpp
@@ -18,7 +18,7 @@
 
 // libc++ actively gets in the way of including <complex.h> from C++, so we
 // have to be naughty.
-#include <../libm/include/complex.h>
+#include <../libc/include/complex.h>
 
 // (libc++ also seems to have really bad implementations of its own that ignore
 // the intricacies of floating point math.)