scons: Fix implicit python dependency discovery on Windows.

Probably due to CRLF endings, the discovery of python import statements
was not working on Windows builds, causing incremental builds to often
fail unless one wiped out the build directory.

NOTE: This is a candidate for stable branches.

scons/custom.py

@@ -95,7 +95,7 @@ def createConvenienceLibBuilder(env):
 
 # TODO: handle import statements with multiple modules
 # TODO: handle from import statements
-import_re = re.compile(r'^import\s+(\S+)$', re.M)
+import_re = re.compile(r'^\s*import\s+(\S+)\s*$', re.M)
 
 def python_scan(node, env, path):
     # http://www.scons.org/doc/0.98.5/HTML/scons-user/c2781.html#AEN2789
@@ -113,6 +113,7 @@ def python_scan(node, env, path):
             if os.path.exists(file):
                 results.append(env.File(file))
                 break
+    #print node, map(str, results)
     return results
 
 python_scanner = SCons.Scanner.Scanner(function = python_scan, skeys = ['.py'])