build: fix windows smp build with gyp

Gyp will try a parallel build if it detect the system has >1 processor.
This functionality depends on the Python "multiprocessing" package. The
multiprocessing package on Windows requires that the top-level module is
importable as a module, see:

  http://docs.python.org/2/library/multiprocessing.html#windows

This fixes issue #984.

README.md

@@ -83,14 +83,14 @@ project tree manually:
 
 Run:
 
-    $ ./gyp_uv -f make
+    $ ./gyp_uv.py -f make
     $ make -C out
 
 ### OS X
 
 Run:
 
-    $ ./gyp_uv -f xcode
+    $ ./gyp_uv.py -f xcode
     $ xcodebuild -project uv.xcodeproj -configuration Release -target All
 
 ### Android

android-configure

@@ -16,5 +16,5 @@ export PLATFORM=android
 
 if [ $2 -a $2 == 'gyp' ]
   then
-    ./gyp_uv -Dtarget_arch=arm -DOS=android
+    ./gyp_uv.py -Dtarget_arch=arm -DOS=android
 fi

vcbuild.bat

@@ -91,7 +91,7 @@ exit /b 1
 
 :have_gyp
 if not defined PYTHON set PYTHON="python"
-%PYTHON% gyp_uv -Dtarget_arch=%target_arch% -Dlibrary=%library%
+%PYTHON% gyp_uv.py -Dtarget_arch=%target_arch% -Dlibrary=%library%
 if errorlevel 1 goto create-msvs-files-failed
 if not exist uv.sln goto create-msvs-files-failed
 echo Project files generated.