special case luabridge for windows/MSVC

luabridge uses static fn addresses to identify classes.
Windows uses different addresses for *identical* static functions
in libardour.dll and ardour.exe

This solves the issue by moving the all functions from a
header-only implementation into libardour.

tools/luadevel/wscript

@@ -33,13 +33,14 @@ def build(bld):
     if bld.is_defined('WINDOWS_VST_SUPPORT') and bld.env['build_target'] != 'mingw':
         return
 
+    if bld.env['build_target'] != 'mingw':
     # TEST/DEVEL TOOL #######################
-    obj = bld (features = 'cxx c cxxprogram')
-    obj.source       = 'devel.cc'
-    obj.target       = 'devel'
-    obj.uselib       = ['SIGCPP', 'READLINE']
-    obj.use          = ['liblua']
-    obj.install_path = None
+        obj = bld (features = 'cxx c cxxprogram')
+        obj.source       = 'devel.cc'
+        obj.target       = 'devel'
+        obj.uselib       = ['SIGCPP', 'READLINE']
+        obj.use          = ['liblua']
+        obj.install_path = None
     #########################################
 
     # commandline luasession wrapper