fix compilation in stable norm, move a platform check to the unit tests

Eigen/src/Core/StableNorm.h

diff --git a/Eigen/src/Core/StableNorm.h b/Eigen/src/Core/StableNorm.h
index facab9d..b4a5d0b 100644
--- a/Eigen/src/Core/StableNorm.h
+++ b/Eigen/src/Core/StableNorm.h
@@ -108,21 +108,15 @@
     iemax = std::numeric_limits<RealScalar>::max_exponent;  // maximum exponent
     rbig  = std::numeric_limits<RealScalar>::max();         // largest floating-point number
 
-    // Check the basic machine-dependent constants.
-    if(iemin > 1 - 2*it || 1+it>iemax || (it==2 && ibeta<5)
-      || (it<=4 && ibeta <= 3 ) || it<2)
-    {
-      ei_assert(false && "the algorithm cannot be guaranteed on this computer");
-    }
     iexp  = -((1-iemin)/2);
-    b1    = RealScalar(std::pow(double(ibeta),iexp));  // lower boundary of midrange
+    b1    = RealScalar(std::pow<RealScalar>(ibeta,iexp));  // lower boundary of midrange
     iexp  = (iemax + 1 - it)/2;
-    b2    = RealScalar(std::pow(double(ibeta),iexp));   // upper boundary of midrange
+    b2    = RealScalar(std::pow<RealScalar>(ibeta,iexp));   // upper boundary of midrange
 
     iexp  = (2-iemin)/2;
-    s1m   = RealScalar(std::pow(double(ibeta),iexp));   // scaling factor for lower range
+    s1m   = RealScalar(std::pow<RealScalar>(ibeta,iexp));   // scaling factor for lower range
     iexp  = - ((iemax+it)/2);
-    s2m   = RealScalar(std::pow(double(ibeta),iexp));   // scaling factor for upper range
+    s2m   = RealScalar(std::pow<RealScalar>(ibeta,iexp));   // scaling factor for upper range
 
     overfl  = rbig*s2m;             // overfow boundary for abig
     eps     = RealScalar(std::pow(double(ibeta), 1-it));

test/stable_norm.cpp

diff --git a/test/stable_norm.cpp b/test/stable_norm.cpp
index 726512e..6ce9947 100644
--- a/test/stable_norm.cpp
+++ b/test/stable_norm.cpp
@@ -33,6 +33,21 @@
   typedef typename MatrixType::Scalar Scalar;
   typedef typename NumTraits<Scalar>::Real RealScalar;
 
+  // Check the basic machine-dependent constants.
+  {
+    int nbig, ibeta, it, iemin, iemax, iexp;
+    RealScalar abig, eps;
+
+    ibeta = std::numeric_limits<RealScalar>::radix;         // base for floating-point numbers
+    it    = std::numeric_limits<RealScalar>::digits;        // number of base-beta digits in mantissa
+    iemin = std::numeric_limits<RealScalar>::min_exponent;  // minimum exponent
+    iemax = std::numeric_limits<RealScalar>::max_exponent;  // maximum exponent
+
+    VERIFY( (!(iemin > 1 - 2*it || 1+it>iemax || (it==2 && ibeta<5) || (it<=4 && ibeta <= 3 ) || it<2))
+           && "the stable norm algorithm cannot be guaranteed on this computer");
+  }
+
+
   int rows = m.rows();
   int cols = m.cols();