doc: Add Compiling section with C++ version and compilers support

Clarification suggested in boostorg/website#562
following discussion about boostorg#526

doc/installation.rst

@@ -1,9 +1,9 @@
 Installation
 ============
 
-The latest version of GIL can be downloaded from https://github.com/boostorg/gil.
+The latest version of Boost.GIL can be downloaded from https://github.com/boostorg/gil.
 
-The GIL is a header-only library. Meaning, it consists of header files only,
+The Boost.GIL is a header-only library. Meaning, it consists of header files only,
 it does not require Boost to be built and it does not require any libraries
 to link against.
 
@@ -13,5 +13,22 @@ to link against.
    which requires client libraries implementing popular image formats
    like libpng, libjpeg, etc.
 
-In order to use GIL, including ``boost/gil.hpp`` and telling your compiler
+In order to use Boost.GIL, including ``boost/gil.hpp`` and telling your compiler
 where to find Boost and GIL headers should be sufficient for most projects.
+
+Compiling
+---------
+
+The Boost.GIL library source code should successfully compile with any
+compiler with complete C++11 support.
+
+.. note::
+
+   We are planning to drop support for require C++14 support in Boost 1.76 or later,
+   or selectively drop support for GCC 5 due to its issues with inheriting constructors,
+   see `discussion for PR #526 <https://github.com/boostorg/gil/pull/526>`_.
+
+For the actual list of currently tested compilers, check results of the library CI
+builds linked from the `README.md <https://github.com/boostorg/gil/blob/develop/README.md>`_
+or inspect the CI services configuration files in the `develop branch <https://github.com/boostorg/gil/tree/develop>`_
+of the library repository.