[tex-k] Errors in indexes to Volume C & E

[胡亚捷 (Hu Yajie)]

Page C354, index entry for `plain METAFONT base'
    Underline both ends of `257--279', for consistency with the rest of
    the index.

Page E571, index entry for `apex_o'
    The variable name should be in italic, not roman.

Page E573, index entry for `cmr10'
    Change `55' to `555'.

Page E577, index entry for `Monotype Corporation'
    If page 209 is mentioned, so should pages 147, 305 and 369.

Not sure about this one:

Page C346, index entry for `,,'
    Add page 57, where exercise 7.6 discusses the unusual meaning of `,,'
    in declarations.