New section in the manual. Amend CHANGES.md and announcement mail

- New subsection "CGAL Dependencies" in the section "Header-only"
- Add a paragraph to CHANGES.md, and to the announcement mail.

Documentation/doc/Documentation/Installation.txt

@@ -352,6 +352,12 @@ cd /path/to/your/code # go to the directory of the code source using \cgal
 cmake -DCGAL_DIR=<CGAL-root> .
 </PRE>
 
+\subsubsection subsection_headeronly_dependencies CGAL Dependencies
+
+\cgal can be used as a header-only library, but no all its dependencies are
+header-only. The libraries \sc{Gmp} and \sc{Mpfr}, for example, are not
+header-only.
+
 \subsubsection subsection_headeronly_pbonwindows Possible Problem on Windows
 
 There is one possible problem when using \cgal in header-only mode on a Windows operating system when compiling a program using several modules (executable programs or dynamic-link libraries DLL). If two different modules use the same static variable, this variable is defined independently in each of these modules. If one module modifies the value of this variable, it will not be modified in the other module, which could induce an unexpected behavior. In \cgal, this concerns only a few specific variables: the <A HREF="https://doc.cgal.org/latest/Generator/classCGAL_1_1Random.html">default random</A>, the <A HREF="https://doc.cgal.org/latest/STL_Extension/group__PkgStlExtensionAssertions.html">failure behavior</A>, <A HREF="https://doc.cgal.org/latest/Stream_support/group__PkgIOstreams.html">IO mode</A>. One example is the following: if you change the default random in one DLL, then if you use the default random in another DLL, you will not obtain the modified default random but the original one.

Installation/CHANGES.md

@@ -24,6 +24,13 @@ Release date: April 2018
     to `Release` manually, to avoid using CGAL libraries without any
     compile-time optimization.
 
+### Header-only mode
+
+- Since CGAL-4.9, it was possible to use CGAL by configuring it using
+  CMake, but without compiling the CGAL libraries. With CGAL-4.11, it is
+  now possible to use CGAL header-only, without even configuring it. CMake
+  is then used only to configure programs using CGAL.
+
 ### 2D Movable Separability of Sets (new package)
 
 -   A new package called "2D Movable Separability of Sets" has been

Maintenance/public_release/announcement/mailing-beta.eml

@@ -1,14 +1,14 @@
-Subject: CGAL 4.12 Beta 1 Released, Computational Geometry Algorithms Library
+Subject: CGAL 4.12 Beta 2 Released, Computational Geometry Algorithms Library
 Content-Type: text/plain; charset="utf-8"
 Body: 
 
-The CGAL Open Source Project is pleased to announce the release 4.12 Beta 1
+The CGAL Open Source Project is pleased to announce the release 4.12 Beta 2
 of CGAL, the Computational Geometry Algorithms Library.
 
 
-CGAL version 4.12 Beta 1 is a public testing release. It should provide
+CGAL version 4.12 Beta 2 is a public testing release. It should provide
 a solid ground to report bugs that need to be tackled before the
-release of the final version of CGAL 4.12 in September.
+release of the final version of CGAL 4.12 in April.
 
 
 *WARNING*: This release features an important change of the CMake scripts
@@ -19,10 +19,21 @@ optimization. Please read the first paragraph of the release notes
 carefully.
 
 
+Note that, since the release CGAL-4.12 Beta 1, the header-only mode of CGAL
+has been modified, and documented.
+
+
 Besides fixes and general enhancement to existing packages, the following
 has changed since CGAL 4.11:
 
 
+Using CGAL Header-only
+
+- It is now possible to use CGAL without configuring it with CMake, as a
+  header-only library. Note that, even if CGAL is header-only, its
+  dependencies (such as GMP and MPFR) are not all header-only.
+
+
 2D Movable Separability of Sets (new package)
 
 -   A new package called "2D Movable Separability of Sets" has been
@@ -39,6 +50,7 @@ has changed since CGAL 4.11:
     orientations of the feasible molds and the corresponding motions
     needed to remove the casted object from the mold.
 
+
 Classification (new package)
 
 -   This package offers an algorithm that classifies a data set into a
@@ -47,6 +59,7 @@ Classification (new package)
     type of data, compute their own local features on the input data
     set, and define their own labels.
 
+
 Kinetic Data Structures (removed package)
 
 -   This package has been removed from CGAL-4.12. Users of the package