move cmake modules to a modules/ subdir

cmake/modules/CheckComplex.cmake

@@ -0,0 +1,22 @@
+INCLUDE(CheckCXXSourceCompiles)
+
+MACRO (CHECK_COMPLEX _RESULT)
+
+SET(_CHECK_COMPLEX_SOURCE_CODE "
+
+#include<complex>
+
+using namespace std;
+
+int main(int argc, char *argv[])
+{
+  complex<double> x(1.0, 1.0);
+  complex<float> y(1.0f, 1.0f);
+  return 0;
+}
+
+")
+
+CHECK_CXX_SOURCE_COMPILES("${_CHECK_COMPLEX_SOURCE_CODE}" ${_RESULT})
+
+ENDMACRO (CHECK_COMPLEX)