Update SourcePawn to master.

This turns on the new expression parser by default.

AMBuildScript

@@ -379,6 +379,16 @@ class SMConfig(object):
   def configure_windows(self, cxx):
     cxx.defines += ['WIN32', '_WINDOWS']
 
+  def add_libamtl(self):
+    # Add libamtl.
+    self.libamtl = {}
+    for arch in self.archs:
+      def get_configure_fn(arch):
+        return lambda builder, name: self.StaticLibrary(builder, name, arch)
+      extra_vars = {'Configure': get_configure_fn(arch)}
+      libamtl = builder.Build('public/amtl/amtl/AMBuilder', extra_vars)
+      self.libamtl[arch] = libamtl.binary
+
   def AddVersioning(self, binary, arch):
     if builder.target.platform == 'windows':
       binary.sources += ['version.rc']
@@ -613,6 +623,7 @@ SM = SMConfig()
 SM.detectProductVersion()
 SM.detectSDKs()
 SM.configure()
+SM.add_libamtl()
 
 if SM.use_auto_versioning():
   SM.generated_headers = builder.Build(