Convert 5 m4 checks to cmake modules

cmake/CheckSysvMath.cmake

@@ -0,0 +1,34 @@
+INCLUDE(CheckCXXSourceCompiles)
+
+MACRO (CHECK_SYSV_MATH _RESULT)
+
+SET(_CHECK_SYSV_MATH_SOURCE_CODE "
+
+#include<cmath>
+
+int main(int argc, char *argv[])
+{
+  double x = 1.0; double y = 1.0;
+  _class(x);
+  ilogb(x);
+  itrunc(x);
+  nearest(x);
+  rsqrt(x);
+  uitrunc(x);
+  
+  copysign(x,y);
+  drem(x,y);
+  fmod(x,y);
+  hypot(x,y);
+  nextafter(x,y);
+  remainder(x,y);
+  scalb(x,y);
+  unordered(x,y);
+  return 0;
+}
+
+")
+
+CHECK_CXX_SOURCE_COMPILES("${_CHECK_SYSV_MATH_SOURCE_CODE}" ${_RESULT})
+
+ENDMACRO (CHECK_SYSV_MATH)