boost program options: win64: bcp namespace renamed version: *.lib file of program_options for *.dll is not created

从 libs/program_options/build/Jamfile.v2 开始，并对照参考的 commit 和 issue 60。使用受支持的 Boost toolchain 复现 program_options 的 Windows shared build，然后验证相应的 import library 是否与 DLL 一起生成；当其在 win32 和 win64 上都能正常工作时，该 issue 即完成。

Between boost 1.63.0 and 1.65.1 line 12 of file 'libs/program_options/build/Jamfile.v2' has been changed:
https://github.com/boostorg/program_options/commit/1f9413f532e58b82d12e9185c2eb8bc45612914c

This change is the reason why the *.lib file for the program_options *.dll file is not created on win64/win32.

Please consider reverting the change mentioned above partially and put back the definition of the flag BOOST_PROGRAM_OPTIONS_DYN_LINK=1:

diff -ruN boost_1_65_1.orig/libs/program_options/build/Jamfile.v2 boost_1_65_1/libs/program_options/build/Jamfile.v2
--- boost_1_65_1.orig/libs/program_options/build/Jamfile.v2	2018-11-20 15:18:48.469951300 +0100
+++ boost_1_65_1/libs/program_options/build/Jamfile.v2	2018-11-22 10:27:15.108147800 +0100
@@ -11,6 +11,10 @@
 
 boost-lib program_options
     : $(SOURCES).cpp
-    : # See https://svn.boost.org/trac/boost/ticket/5049
+    : <link>shared:<define>BOOST_PROGRAM_OPTIONS_DYN_LINK=1 # tell source we're building dll's
+      # See https://svn.boost.org/trac/boost/ticket/5049
       <target-os>hpux,<toolset>gcc:<define>_INCLUDE_STDC__SOURCE_199901
-    ;
\ No newline at end of file
+    :
+    : <link>shared:<define>BOOST_PROGRAM_OPTIONS_DYN_LINK=1
+    ;
+

Similar to issue: https://github.com/boostorg/program_options/issues/60