Add documentation for ibmcxx toolset. Remove old/untested vacpp and xlcpp toolsets now that they are replaced by ibmcxx toolset.

Author: grafikrobot

doc/src/history.adoc

@@ -3,6 +3,9 @@
 
 == Version 5.3.0
 
+* *New*: Replace the old `vacpp` and `xlcpp` with a new `ibmcxx` toolset that
+  supports the old compilers and the new "IBM XL" and  "IBM Open XL" compilers.
+  -- _René Ferdinand Rivera Morell_ and _Chris Ward_
 * Fix command database output file path when an output dir is not given.
   -- _René Ferdinand Rivera Morell_
 * Fix asciidoctor ignoring relevant features when building which caused invalid

doc/src/reference.adoc

@@ -338,7 +338,6 @@ include::../../src/tools/ibmcxx.jam[tag=doc]
 include::../../src/tools/intel.jam[tag=doc]
 include::../../src/tools/msvc.jam[tag=doc]
 include::../../src/tools/sun.jam[tag=doc]
-include::../../src/tools/vacpp.jam[tag=doc]
 :leveloffset: -3
 
 === Third-party libraries

src/tools/ibmcxx.jam

@@ -1,5 +1,5 @@
 #|
-Copyright René Ferdinand Rivera Morell 2024
+Copyright René Ferdinand Rivera Morell 2024-2025
 Distributed under the Boost Software License, Version 1.0.
 (See accompanying file LICENSE.txt
 or copy at https://www.bfgroup.xyz/b2/LICENSE.txt)
@@ -20,6 +20,24 @@ The module is initialized using the following syntax:
 using ibmcxx : [version] : [c++-compile-command] : [compiler options] ;
 ----
 
+This statement may be repeated several times, if you want to configure
+several versions of the compiler.
+
+Without a version or command B2 will attempt to find a compiler that matches
+the options in various standard install location, including in the `PATH`.
+
+The following options can be provided, using
+_`<option-name>option-value syntax`_:
+
+`tool`::
+Indicates the type of frontend the compiler is. The values can be `clang` or
+`ibm`. The `clang` frontend corresponds to the Open XL >= 17.x versions. And
+the `ibm` frontend corresponds to XL <= 16.x.
+
+If you have multiple compilers configured as separate frontends one can select
+the specific one by instead of using the base `ibmcxx` toolset name using
+extended `ibmcxx-clang` or `ibmcxx-ibm` names.
+
 |# # end::doc[]
 
 import toolset : flags ;