First step for compiling plugin DLLs with MSVC nmake. The hdimage plugin
(bx_hdimage.dll) can be built now. All plugins that require special rules
could be fixed for nmake in a similar way.
TODO: find a way to compile plugins with standard rules (GNU make uses bx_%.dll
in that case, but MSVC nmake doesn't support this syntax).


git-svn-id: svn://svn.code.sf.net/p/bochs/code/trunk@12287 6c8e4198-a580-4521-a02f-c9ae86df1db9