Revert "attempted fix for android build"

This reverts commit c3acead3, now that
cc906ec4 "The Android NDK for some reason don't
have these math functions in std::" uses all the declarations from <math.h>
instead of <cmath>.

sal/rtl/math.cxx

@@ -36,7 +36,6 @@
 #include <limits.h>
 #include <math.h>
 #include <stdlib.h>
-#include <cmath>
 
 static int const n10Count = 16;
 static double const n10s[2][n10Count] = {