Require recent GCC and MSCV and removed EIGEN_HAS_CXX14 and some other feature test macros

doc/PreprocessorDirectives.dox

@@ -55,23 +55,17 @@ By default, %Eigen strive to automatically detect and enable language features a
 the information provided by the compiler.
 
  - \b EIGEN_MAX_CPP_VER - disables usage of C++ features requiring a version greater than EIGEN_MAX_CPP_VER.
-   Possible values are: 11, 14, 17, etc. If not defined (the default), %Eigen enables all features supported
+   Possible values are: 14, 17, etc. If not defined (the default), %Eigen enables all features supported
    by the compiler.
 
 Individual features can be explicitly enabled or disabled by defining the following token to 0 or 1 respectively.
-For instance, one might limit the C++ version to C++03 by defining EIGEN_MAX_CPP_VER=03, but still enable C99 math
+For instance, one might limit the C++ version to C++14 by defining EIGEN_MAX_CPP_VER=14, but still enable C99 math
 functions by defining EIGEN_HAS_C99_MATH=1.
 
  - \b EIGEN_HAS_C99_MATH - controls the usage of C99 math functions such as erf, erfc, lgamma, etc.
-   Automatic detection disabled if EIGEN_MAX_CPP_VER<11.
  - \b EIGEN_HAS_CXX11_MATH - controls the implementation of some functions such as round, logp1, isinf, isnan, etc.
-   Automatic detection disabled if EIGEN_MAX_CPP_VER<11.
  - \b EIGEN_HAS_STD_RESULT_OF - defines whether std::result_of is supported
-   Automatic detection disabled if EIGEN_MAX_CPP_VER<11.
- - \b EIGEN_HAS_VARIADIC_TEMPLATES - defines whether variadic templates are supported
-   Automatic detection disabled if EIGEN_MAX_CPP_VER<11.
  - \b EIGEN_HAS_CONSTEXPR - defines whether relaxed const expression are supported
-   Automatic detection disabled if EIGEN_MAX_CPP_VER<14.
  - \b EIGEN_NO_IO - Disables any usage and support for `<iostreams>`.
 
 \section TopicPreprocessorDirectivesAssertions Assertions

doc/snippets/Slicing_rawarray_cxx11.cpp

@@ -1,5 +1,3 @@
-#if EIGEN_HAS_STATIC_ARRAY_TEMPLATE
 MatrixXi A = MatrixXi::Random(4,6);
 cout << "Initial matrix A:\n" << A << "\n\n";
 cout << "A(all,{4,2,5,5,3}):\n" << A(all,{4,2,5,5,3}) << "\n\n";
-#endif