Add cef_api_hash.h generated by the translator tool (see issue #2596)

This splits out the API hashes from the cef_version.h file which is generated at
build time. Changes to the cef_api_hash.h file are committed to the repo and
represent potentially breaking API changes. This commit history will be used to
calculate the version number.

tools/cef_api_hash.py

@@ -44,6 +44,7 @@ class cef_api_hash:
     self.included_files = []
 
     self.excluded_files = [
+        "cef_api_hash.h",
         "cef_version.h",
         "internal/cef_tuple.h",
         "internal/cef_types_wrappers.h",