Use shall instead of md5

Performance is not affected here. This is needed to make the quantifiedcode linter happy.
As there is not much difference between the two, sha1 seems OK and can be used instead.

Author: iMichka

pygccxml/parser/declarations_cache.py

@@ -22,7 +22,7 @@ def file_signature(filename):
     # Extend here to use md5 hash for signature
     # - This change allows duplicate auto-generated files to be recognized
 
-    sig = hashlib.md5()
+    sig = hashlib.sha1()
     with open(filename, "rb") as f:
         buf = f.read()
         sig.update(buf)
@@ -38,7 +38,7 @@ def configuration_signature(config):
         to be different between runs.
     """
 
-    sig = hashlib.md5()
+    sig = hashlib.sha1()
     if isinstance(config, cxx_parsers_cfg.xml_generator_configuration_t):
         sig.update(str(config.xml_generator_path).encode())
     sig.update(str(config.working_directory).encode('utf-8'))