wallet: Add new htlc column "localfailmsg" for outgoing htlcs.

We're going to change our internal structure next, so this is preparation.
We populate existing errors with temporary node failures, for simplicity.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

devtools/sql-rewrite.py

@@ -41,6 +41,8 @@ class Sqlite3Rewriter(Rewriter):
             r'BIGSERIAL': 'INTEGER',
             r'CURRENT_TIMESTAMP\(\)': "strftime('%s', 'now')",
             r'INSERT INTO[ \t]+(.*)[ \t]+ON CONFLICT.*DO NOTHING;': 'INSERT OR IGNORE INTO \\1;',
+            # Rewrite "decode('abcd', 'hex')" to become "x'abcd'"
+            r'decode\((.*),\s*[\'\"]hex[\'\"]\)': 'x\\1',
         }
         return self.rewrite_types(query, typemapping)