install broken for treelang

[David Edelsohn]

	My AIX systems have an old Makeinfo that cannot build the GCC
documents.  I am seeing errors because info files do not exist:

make[1]: *** No rule to make target `/farm/dje/install/powerpc-ibm-aix5.1.0.0-20031020/info/g77.info', needed by `install-info'.  Stop.
make[1]: Leaving directory `/tmp2/powerpc-ibm-aix5.1.0.0-20031020/gcc'
make: *** [install-gcc] Error 2
gcc_build: error: Installation failed