depcomp: support tcc (Tiny C Compiler)

depcomp: support tcc (Tiny C Compiler)

This change fixes automake bug#11007.

Since git commit 0c928da9 of 21-06-2010, "tcc: Draft suppoprt for
-MD/-MF options" (sic, with typo in summary line), tcc has supported
automatic dependency generation with a command-line interface
similar to what old (pre-8.0) Intel compilers did.  This caused
Automake-generated code for automatic dependency tracking to
recognize tcc dependency style as "icc".  However, the format of
the dependency files generated by tcc is apparently different enough
from that of icc to cause spurious failures in the post-processing
operated by our 'depcomp' script on such files.

The failure was exposed with the development version of tcc 0.9.26
(as installed with debian package "tcc 0.9.26~git20120104.83d") by
test case 'depcomp-auto.tap' (available only in the master branch).

* lib/depcomp (icc): Cater to tcc as well.  Update comments
accordingly.
* NEWS: Update.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>