scripted-diff: Replace error() with LogError()

This fixes the log output when -logsourcelocations is used.

Also, instead of 'ERROR:', the log will now say '[error]', like other
errors logged with LogError.

-BEGIN VERIFY SCRIPT-
 sed -i --regexp-extended 's!  error\("([^"]+)"!  LogError("\1\\n"!g' $( git grep -l '  error(' ./src/ )
-END VERIFY SCRIPT-

src/index/base.cpp

@@ -229,7 +229,7 @@ bool BaseIndex::Commit()
         }
     }
     if (!ok) {
-        error("%s: Failed to commit latest %s state", __func__, GetName());
+        LogError("%s: Failed to commit latest %s state\n", __func__, GetName());
         return false;
     }
     return true;