Highlighting New Keywords in texinfo-mode

[Christopher Dimech]

I want to highlight new keywords such as \quad \over \ cos

Using the following command seems to work, however still some are not properly 
highlighted

 ( font-lock-add-keywords 'texinfo-mode
     '( ("\\quad" . font-lock-keyword-face)
        ("\\over" . font-lock-keyword-face)
        ("\\theta" . font-lock-keyword-face)
        ("\\omega" . font-lock-keyword-face)
        ("\\cos" . font-lock-keyword-face)
   )
 )