fix bug 475: .exp() now returns +inf when overflow occurs (SSE)

(transplanted from dbd64aae279527f558021ce98c0950402443d460)

--HG--
branch : 3.0
extra : transplant_source : %DB%D6J%AE%27%95%27%F5X%02%1C%E9%8C%09P%40%24C%D4%60

Author: ggael

Eigen/src/Core/arch/SSE/MathFunctions.h

@@ -121,7 +121,7 @@ Packet4f pexp<Packet4f>(const Packet4f& _x)
   _EIGEN_DECLARE_CONST_Packet4i(0x7f, 0x7f);
 
 
-  _EIGEN_DECLARE_CONST_Packet4f(exp_hi, 88.3762626647949f);
+  _EIGEN_DECLARE_CONST_Packet4f(exp_hi,  88.3762626647950f);
   _EIGEN_DECLARE_CONST_Packet4f(exp_lo, -88.3762626647949f);
 
   _EIGEN_DECLARE_CONST_Packet4f(cephes_LOG2EF, 1.44269504088896341f);
@@ -168,7 +168,7 @@ Packet4f pexp<Packet4f>(const Packet4f& _x)
   y = pmadd(y, z, x);
   y = padd(y, p4f_1);
 
-  /* build 2^n */
+  // build 2^n
   emm0 = _mm_cvttps_epi32(fx);
   emm0 = _mm_add_epi32(emm0, p4i_0x7f);
   emm0 = _mm_slli_epi32(emm0, 23);