Add support for modular build structure. (#2905)

* Use beast exclusive valgrind feature.

* Make the library modular usable.

* Switch to library requirements instead of source. As source puts extra source in install targets.

* Add Beast root dir for includes. As some tests refer to files relative to that.

* Replace relative docca refs with project based.

* Avoid mtuliple openssl configurations.

* Always declare openssl. If it's empty and duplicate it will be ignored.

* Add missing import-search for cconfig/predef checks.

* Add requires-b2 check to top-level build file.

* Bump B2 require to 5.2

* Update copyright dates.

* Move inter-lib dependencies to a project variable and into the build targets.

* Update build deps.

* Update build deps.

* The http/client/body example uses the source header from json instead of the linked library.

test/Jamfile

@@ -8,17 +8,8 @@
 #
 
 import testing ;
-import ../../config/checks/config : requires ;
-
-lib lib-test
-    : lib_test.cpp
-    : requirements
-    <link>static
-    $(defines)
-    : usage-requirements
-    <include>./extras/include
-    $(defines)
-    ;
+import-search /boost/config/checks ;
+import config : requires ;
 
 project /boost/beast/test
     : requirements
@@ -34,12 +25,21 @@ project /boost/beast/test
     <target-os>darwin:<define>Z_HAVE_UNISTD_H=1
     <library>/boost/beast//lib-asio/<link>static
     <boost.beast.separate-compilation>on:<library>/boost/beast//lib-beast/<link>static
-    <library>/boost/filesystem//boost_filesystem
-    <library>/boost/context//boost_context
+    <library>/boost/filesystem//boost_filesystem/<link>static
+    <library>/boost/context//boost_context/<link>static
     <address-sanitizer>norecover:<context-impl>ucontext
     <address-sanitizer>norecover:<define>BOOST_USE_ASAN=1
+    <include>..
   ;
 
+lib lib-test
+    : lib_test.cpp
+    : requirements
+    <link>static
+    : usage-requirements
+    <include>extras/include
+    ;
+
 lib lib-zlib :
     extern/zlib-1.2.12/adler32.c
     extern/zlib-1.2.12/compress.c

test/bench/parser/Jamfile

@@ -7,10 +7,11 @@
 # Official repository: https://github.com/boostorg/beast
 #
 
+project : requirements <library>/boost/beast/test//lib-test ;
+
 run
     nodejs_parser.cpp
     bench_parser.cpp
-    /boost/beast/test//lib-test
     : : : :
     bench-parser ;
 

test/doc/Jamfile

@@ -7,6 +7,10 @@
 # Official repository: https://github.com/boostorg/beast
 #
 
+project
+    : requirements
+        <include>../.. ;
+
 local libs =
     /boost/beast//lib-asio-ssl
     /boost/beast/test//lib-test

test/example/common/Jamfile

@@ -7,6 +7,10 @@
 # Official repository: https://github.com/boostorg/beast
 #
 
+project
+    : requirements
+        <include>../../.. ;
+
 local SOURCES =
     root_certificates.cpp
     server_certificate.cpp