[Patch, committed] libcilkrts - add AM_MAINTAINER_MODE; update "gcc_update" for libcilkrts

[Tobias Burnus]

I have committed the following as obvious:

* Added AM_MAINTAINER_MODE to libcilkrtl's configure.ac (and reconfigured)
Before, building failed on a system which had the wrong version of autoconf.
* As suggested by Joseph, I added the relevant files for libcilkrtl to 
contrib/gcc_update

Committed as Rev. 204189.

Tobias