Add missing 'f' in float literal in SpecialFunctionsImpl.h that triggers implicit conversion warning.

unsupported/Eigen/src/SpecialFunctions/SpecialFunctionsImpl.h

diff --git a/unsupported/Eigen/src/SpecialFunctions/SpecialFunctionsImpl.h b/unsupported/Eigen/src/SpecialFunctions/SpecialFunctionsImpl.h
index 5d84701..03a50d3 100644
--- a/unsupported/Eigen/src/SpecialFunctions/SpecialFunctionsImpl.h
+++ b/unsupported/Eigen/src/SpecialFunctions/SpecialFunctionsImpl.h
@@ -324,7 +324,7 @@
   const T beta_6 = pset1<T>(0.014070470171167667f);
   const T beta_8 = pset1<T>(0.0010179625278914885f);
   const T beta_10 = pset1<T>(0.000023547966471313185f);
-  const T beta_12 = pset1<T>(-1.1791602954361697e-7);
+  const T beta_12 = pset1<T>(-1.1791602954361697e-7f);
 
   // Since the polynomials are odd/even, we need x^2.
   const T x2 = pmul(x, x);