0032921: Configuration, CMake - allow selecting C++ standard.

Make C++ standard to be enable from cmake settings:

User will be able choosing C++ language standard by selecting cmake variable BUILD_CPP_STANDARD.
For correct working, CMAKE_CXX_STANDARD cmake built-in variable should be available.
To enable CMAKE_CXX_STANDARD, minimum CMAKE version has been updated to 3.1.

Available next standard items:
C++11
C++14
C++17
C++20
C++23

This issue consists from several steps to achive main goal:
1) Configuratiuon, CMake - allow selecting C++ standard.
2) Require minimum CMAKE version 3.1 (for enabling CMAKE_CXX_STANDARD).
3) More flexible CMAKE_CXX_COMPILER_ID identification (fixups previous commit!)
4) Add description of new CMAKE variable `BUILD_CPP_STANDARD` into documentation.
5) Update CMAKE requirements in documentation.
6) Set C++11 standard for several projects.

samples/mfc/standard/01_Geometry/CMakeLists.txt

@@ -1,4 +1,10 @@
-cmake_minimum_required (VERSION 2.6)
+# Caution! Be careful, when increase minimal cmake version:
+# using of newer version may leads (by default) to applying
+# of some new policies. It may break compilation.
+# For canceling of applying new policies use:
+# cmake_policy(PUSH) before `cmake_minimum_required`
+# and cmake_policy(POP) after.
+cmake_minimum_required (VERSION 3.1 FATAL_ERROR)
 
 project (Geometry)
 

samples/mfc/standard/02_Modeling/CMakeLists.txt

@@ -1,4 +1,10 @@
-cmake_minimum_required (VERSION 2.6)
+# Caution! Be careful, when increase minimal cmake version:
+# using of newer version may leads (by default) to applying
+# of some new policies. It may break compilation.
+# For canceling of applying new policies use:
+# cmake_policy(PUSH) before `cmake_minimum_required`
+# and cmake_policy(POP) after.
+cmake_minimum_required (VERSION 3.1 FATAL_ERROR)
 
 project (Modeling)
 

samples/mfc/standard/03_ImportExport/CMakeLists.txt

@@ -1,4 +1,10 @@
-cmake_minimum_required (VERSION 2.6)
+# Caution! Be careful, when increase minimal cmake version:
+# using of newer version may leads (by default) to applying
+# of some new policies. It may break compilation.
+# For canceling of applying new policies use:
+# cmake_policy(PUSH) before `cmake_minimum_required`
+# and cmake_policy(POP) after.
+cmake_minimum_required (VERSION 3.1 FATAL_ERROR)
 
 project (ImportExport)
 

samples/mfc/standard/04_HLR/CMakeLists.txt

@@ -1,4 +1,10 @@
-cmake_minimum_required (VERSION 2.6)
+# Caution! Be careful, when increase minimal cmake version:
+# using of newer version may leads (by default) to applying
+# of some new policies. It may break compilation.
+# For canceling of applying new policies use:
+# cmake_policy(PUSH) before `cmake_minimum_required`
+# and cmake_policy(POP) after.
+cmake_minimum_required (VERSION 3.1 FATAL_ERROR)
 
 project (HLR)
 

samples/mfc/standard/mfcsample/CMakeLists.txt

@@ -1,4 +1,10 @@
-cmake_minimum_required (VERSION 2.6)
+# Caution! Be careful, when increase minimal cmake version:
+# using of newer version may leads (by default) to applying
+# of some new policies. It may break compilation.
+# For canceling of applying new policies use:
+# cmake_policy(PUSH) before `cmake_minimum_required`
+# and cmake_policy(POP) after.
+cmake_minimum_required (VERSION 3.1 FATAL_ERROR)
 
 project (mfcsample)