add documentation for CheckCXX11StringSupport

cmake/CheckCXX11StringSupport.cmake

@@ -1,3 +1,41 @@
+# This file is part of snapcast
+# Copyright (C) 2014-2018  Johannes Pohl
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+#[=======================================================================[.rst:
+CheckCXX11StringSupport
+----------------------
+
+Check if the C++ compiler supports std::to_string, std::stoi, ...
+See also: https://stackoverflow.com/questions/17950814/how-to-use-stdstoul-and-stdstoull-in-android/18124627#18124627
+
+.. command:: CHECK_CXX11_STRING_SUPPORT
+
+  ::
+
+    CHECK_CXX11_STRING_SUPPORT(resultVar)
+
+  Checks support for std::to_string, std::stoul, std::stoi, std::stod.
+  The result will be stored in the internal cache variable specified
+  by ``resultVar``, with a boolean true value for success and boolean false for
+  failure.
+#]=======================================================================]
+
+
+include_guard(GLOBAL)
+
 include(CheckCXXSourceCompiles)
 
 macro (CHECK_CXX11_STRING_SUPPORT _RESULT)