Close #24508: Backport the 3.5 MSBuild project files.

The old project files move to PC/VS9.0 and remain supported.

VS2008 is still required to build 2.7; VS2010 (or later, plus Windows SDK 7.1)
is *also* required to use the new project files.
diff --git a/PC/VS9.0/rmpyc.py b/PC/VS9.0/rmpyc.py
new file mode 100644
index 0000000..a1e75bb
--- /dev/null
+++ b/PC/VS9.0/rmpyc.py
@@ -0,0 +1,25 @@
+# Remove all the .pyc and .pyo files under ../Lib.
+
+
+def deltree(root):
+    import os
+    from os.path import join
+
+    npyc = npyo = 0
+    for root, dirs, files in os.walk(root):
+        for name in files:
+            delete = False
+            if name.endswith('.pyc'):
+                delete = True
+                npyc += 1
+            elif name.endswith('.pyo'):
+                delete = True
+                npyo += 1
+
+            if delete:
+                os.remove(join(root, name))
+
+    return npyc, npyo
+
+npyc, npyo = deltree("../Lib")
+print(npyc, ".pyc deleted,", npyo, ".pyo deleted")