new modules 'mbchar', 'mbiter', 'mbfile', 'strnlen1'

[Bruno Haible]

Hi,

Prompted by the need to implement a correct strcasecmp() function, I
added to gnulib the modules:

  - mbchar: Multibyte character data type.
  - mbiter: Iterating through multibyte strings.
  - mbfile: Multibyte character I/O.

These modules were written in 2001, mbchar and mbiter by me, mbfile by
me and Mitsuru Chinen.

  - strnlen1: A variant of strnlen.

I don't attach the source here; you can obtain them from the CVS.
But please proofread and comment on it!

Bruno