Help: Document VS and Xcode toolset selection

Add explicit sections to the individual generator documentation to cover
the `cmake -T` option along with the default behavior for each
generator.

Help/generator/Visual Studio 10 2010.rst

@@ -17,3 +17,10 @@ a target platform name optionally at the end of this generator name:
 
 For compatibility with CMake versions prior to 3.0, one may specify this
 generator using the name ``Visual Studio 10`` without the year component.
+
+Toolset Selection
+^^^^^^^^^^^^^^^^^
+
+The ``v100`` toolset that comes with Visual Studio 10 2010 is selected by
+default.  The :variable:`CMAKE_GENERATOR_TOOLSET` option may be set, perhaps
+via the :manual:`cmake(1)` ``-T`` option, to specify another toolset.

Help/generator/Visual Studio 11 2012.rst

@@ -20,3 +20,10 @@ a target platform name optionally at the end of this generator name:
 
 For compatibility with CMake versions prior to 3.0, one may specify this
 generator using the name "Visual Studio 11" without the year component.
+
+Toolset Selection
+^^^^^^^^^^^^^^^^^
+
+The ``v110`` toolset that comes with Visual Studio 11 2012 is selected by
+default.  The :variable:`CMAKE_GENERATOR_TOOLSET` option may be set, perhaps
+via the :manual:`cmake(1)` ``-T`` option, to specify another toolset.

Help/generator/Visual Studio 12 2013.rst

@@ -17,3 +17,10 @@ a target platform name optionally at the end of this generator name:
 
 For compatibility with CMake versions prior to 3.0, one may specify this
 generator using the name "Visual Studio 12" without the year component.
+
+Toolset Selection
+^^^^^^^^^^^^^^^^^
+
+The ``v120`` toolset that comes with Visual Studio 12 2013 is selected by
+default.  The :variable:`CMAKE_GENERATOR_TOOLSET` option may be set, perhaps
+via the :manual:`cmake(1)` ``-T`` option, to specify another toolset.

Help/generator/Visual Studio 14 2015.rst

@@ -14,3 +14,10 @@ a target platform name optionally at the end of this generator name:
 
 ``Visual Studio 14 2015 ARM``
   Specify target platform ``ARM``.
+
+Toolset Selection
+^^^^^^^^^^^^^^^^^
+
+The ``v140`` toolset that comes with Visual Studio 14 2015 is selected by
+default.  The :variable:`CMAKE_GENERATOR_TOOLSET` option may be set, perhaps
+via the :manual:`cmake(1)` ``-T`` option, to specify another toolset.

Help/generator/Visual Studio 15.rst

@@ -14,3 +14,10 @@ a target platform name optionally at the end of this generator name:
 
 ``Visual Studio 15 ARM``
   Specify target platform ``ARM``.
+
+Toolset Selection
+^^^^^^^^^^^^^^^^^
+
+The ``v141`` toolset that comes with Visual Studio 15 is selected by
+default.  The :variable:`CMAKE_GENERATOR_TOOLSET` option may be set, perhaps
+via the :manual:`cmake(1)` ``-T`` option, to specify another toolset.

Help/generator/Xcode.rst

@@ -2,3 +2,10 @@ Xcode
 -----
 
 Generate Xcode project files.
+
+Toolset Selection
+^^^^^^^^^^^^^^^^^
+
+By default Xcode is allowed to select its own default toolchain.
+The :variable:`CMAKE_GENERATOR_TOOLSET` option may be set, perhaps
+via the :manual:`cmake(1)` ``-T`` option, to specify another toolset.

Help/manual/OPTIONS_BUILD.txt

@@ -52,13 +52,12 @@
  Specify toolset name if supported by generator.
 
  Some CMake generators support a toolset name to be given to the
- native build system to choose a compiler.  This is supported only on
- specific generators:
-
- ::
+ native build system to choose a compiler.
+ See the :variable:`CMAKE_GENERATOR_TOOLSET` variable.
+ This is supported only on specific generators:
 
-   Visual Studio >= 10
-   Xcode >= 3.0
+ * :ref:`Visual Studio Generators` for VS 2010 and above
+ * The :generator:`Xcode` generator for Xcode 3.0 and above
 
  See native build system documentation for allowed toolset names.