genlib: Warn if using dlltool and support newer VS versions than 2010

If we generate .lib files with dlltool, they won't work very well with
Visual Studio and can result in missing symbols.

https://sourceware.org/bugzilla/show_bug.cgi?id=12633

https://bugzilla.gnome.org/show_bug.cgi?id=773889

cerbero/ide/vs/genlib.py

@@ -20,6 +20,7 @@ import os
 
 from cerbero.config import Architecture
 from cerbero.utils import shell, to_unixpath
+from cerbero.utils import messages as m
 
 
 class GenLib(object):
@@ -58,13 +59,17 @@ class GenLib(object):
                 arch = 'x64'
             shell.call(self.LIB_TPL % (lib_path, defname, implib, arch), outputdir)
         else:
+            m.warning("Using dlltool instead of lib.exe! Resulting .lib files"
+                " will have problems with Visual Studio, see "
+                " http://sourceware.org/bugzilla/show_bug.cgi?id=12633")
             shell.call(self.DLLTOOL_TPL % (defname, implib, dllname), outputdir)
         return os.path.join(outputdir, implib)
 
     def _get_vc_tools_path(self):
-        if 'VS100COMNTOOLS' in os.environ:
-            path = os.path.join(os.environ['VS100COMNTOOLS'], '..', '..',
-                'VC', 'bin', 'amd64')
-            if os.path.exists (path):
-                return path
+        for version in ['100', '110', '120', '130', '140', '150']:
+            variable = 'VS{0}COMNTOOLS'.format(version)
+            if variable in os.environ:
+                path = os.path.join(os.environ[variable], '..', '..', 'VC', 'bin', 'amd64')
+                if os.path.exists (path):
+                    return path
         return None