removed troublesome M_PI and M_PIl constants

unsupported/test/FFT.cpp

diff --git a/unsupported/test/FFT.cpp b/unsupported/test/FFT.cpp
index 4a6d495..3e41265 100644
--- a/unsupported/test/FFT.cpp
+++ b/unsupported/test/FFT.cpp
@@ -45,13 +45,10 @@
         long double totalpower=0;
         long double difpower=0;
         cerr <<"idx\ttruth\t\tvalue\t|dif|=\n";
+        long double pi = acos(-1);
         for (size_t k0=0;k0<size_t(fftbuf.size());++k0) {
             complex<long double> acc = 0;
-#ifdef _GNU_SOURCE
-            long double phinc = -2.*k0* M_PIl / timebuf.size();
-#else
-            long double phinc = -2.*k0* M_PI / timebuf.size();
-#endif
+            long double phinc = -2.*k0* pi / timebuf.size();
             for (size_t k1=0;k1<size_t(timebuf.size());++k1) {
                 acc +=  promote( timebuf[k1] ) * exp( complex<long double>(0,k1*phinc) );
             }

unsupported/test/FFTW.cpp

diff --git a/unsupported/test/FFTW.cpp b/unsupported/test/FFTW.cpp
index cf7be75..fdb41f2 100644
--- a/unsupported/test/FFTW.cpp
+++ b/unsupported/test/FFTW.cpp
@@ -45,10 +45,11 @@
     {
         long double totalpower=0;
         long double difpower=0;
+        long double pi = acos(-1);
         cerr <<"idx\ttruth\t\tvalue\t|dif|=\n";
         for (size_t k0=0;k0<fftbuf.size();++k0) {
             complex<long double> acc = 0;
-            long double phinc = -2.*k0* M_PIl / timebuf.size();
+            long double phinc = -2.*k0* pi / timebuf.size();
             for (size_t k1=0;k1<timebuf.size();++k1) {
                 acc +=  promote( timebuf[k1] ) * exp( complex<long double>(0,k1*phinc) );
             }