Fix checking the wrong directory for smsdk_ext.cpp. Updated some comments.

public/sample_ext/AMBuildScript

@@ -1,9 +1,7 @@
 # vim: set sts=2 ts=8 sw=2 tw=99 et ft=python:
 import os, sys
 
-###############
-# Make sure to edit PackageScript, which copies your files to their appropriate locations
-# Simple extensions do not need to modify past this point.
+# Simple extensions do not need to modify this file.
 
 class SDK(object):
   def __init__(self, sdk, ext, aDef, name, platform, dir):

public/sample_ext/AMBuilder

@@ -3,16 +3,20 @@ import os, sys
 
 projectName = 'sample'
 
-#smsdk_ext.cpp will be automatically added later
+# smsdk_ext.cpp will be automatically added later
 sourceFiles = [
   'extension.cpp',
 ]
 
+###############
+# Make sure to edit PackageScript, which copies your files to their appropriate locations
+# Simple extensions do not need to modify past this point.
+
 project = Extension.HL2Project(builder, projectName + '.ext')
 
-if os.path.isfile(os.path.join(builder.currentSourcePath, 'smsdk_ext.cpp')):
+if os.path.isfile(os.path.join(builder.currentSourcePath, 'sdk', 'smsdk_ext.cpp')):
   # Use the copy included in the project
-  project.sources += ['smsdk_ext.cpp']
+  project.sources += [os.path.join('sdk', 'smsdk_ext.cpp')]
 else:
   # Use the copy included with SM 1.6 and newer
   project.sources += [os.path.join(Extension.sm_root, 'public', 'smsdk_ext.cpp')]

public/sample_ext/configure.py

@@ -2,6 +2,8 @@
 import sys
 from ambuild2 import run
 
+# Simple extensions do not need to modify this file.
+
 builder = run.PrepareBuild(sourcePath = sys.path[0])
 
 builder.options.add_option('--hl2sdk-root', type=str, dest='hl2sdk_root', default=None,