Require a C++11 compiler to build the C++ wrappers (#693)

* Committing clang-format changes

* Requires a C++11 compiler to build the C++ wrappers

Co-authored-by: github-actions <41898282+github-actions[bot]@users.noreply.github.com>

config/clang-cxxflags

@@ -113,19 +113,7 @@ if test "X-clang" = "X-$cxx_vendor" -o "X-Apple LLVM" = "X-$cxx_vendor"; then
             ;;
     esac
 
-    case "$host_os-$host_cpu" in
-        # cygwin needs the "-std=c99" flag removed, so make
-        # a specific case for Cygwin without the flag and a default
-        # case to add the flag everywhere else
-        cygwin-*)
-            ;;
-
-        *)
-            H5_CXXFLAGS="$H5_CXXFLAGS -std=c++11"
-            ;;
-    esac
-
-    H5_CXXFLAGS="$H5_CXXFLAGS $arch"
+    H5_CXXFLAGS="$H5_CXXFLAGS $arch -std=c++11"
 
     ##############
     # Production #

config/cmake/HDFCXXCompilerFlags.cmake

@@ -9,7 +9,7 @@
 # If you do not have access to either file, you may request a copy from
 # help@hdfgroup.org.
 #
-set(CMAKE_CXX_STANDARD 98)
+set(CMAKE_CXX_STANDARD 11)
 set(CMAKE_CXX_STANDARD_REQUIRED TRUE)
 set(CMAKE_CXX_EXTENSIONS OFF)
 

config/gnu-cxxflags

@@ -119,7 +119,7 @@ if test "X-g++" = "X-$cxx_vendor"; then
     esac
 
     # C++-specific
-    H5_CXXFLAGS="$H5_CXXFLAGS $arch"
+    H5_CXXFLAGS="$H5_CXXFLAGS $arch -std=c++11"
 
     ##############
     # Production #

release_docs/RELEASE.txt

@@ -49,6 +49,14 @@ New Features
 
     Configuration:
     -------------
+    - A C++11-compliant compiler is now required to build the C++ wrappers
+
+      CMAKE_CXX_STANDARD is now set to 11 when building with CMake and 
+      -std=c++11 is added when building with clang/gcc via the Autotools.
+
+      (DER - 2021/05/27)
+
+
     - CMake will now run the shell script tests in test/ by default
 
       The test directory includes several shell script tests that previously