font-patcher: Fix incomplete separation of naming and patching

[why]
The font_patcher object should be self contained, and code outside of it
should not depend on stuff done within it that does not have to do
anything with patching.
In fact the code should run even if font_patcher.patch() has not been
called.

[how]
Pull name backup out of the patching process.

Signed-off-by: Fini Jastrow <ulf.fini.jastrow@desy.de>

font-patcher

@@ -334,7 +334,6 @@ class font_patcher:
         self.sourceFont = font
         self.setup_version()
         self.get_essential_references()
-        self.setup_name_backup(font)
         self.assert_monospace()
         self.remove_ligatures()
         self.get_sourcefont_dimensions()
@@ -2007,6 +2006,7 @@ def main():
                 subfont)
             sys.exit(1)
 
+        patcher.setup_name_backup(sourceFonts[-1])
         patcher.patch(sourceFonts[-1])
 
     print("Done with Patch Sets, generating font...")