install-only distributions probably don't need .a files

[geofft]

$ find . -name \*.a -exec du -ch {} +
148K	./lib/thread2.8.9/libthread2.8.9.a
492K	./lib/Tix8.4.3/libTix8.4.3.a
516K	./lib/itcl4.2.4/libitcl4.2.4.a
4.0K	./lib/itcl4.2.4/libitclstub4.2.4.a
1.2M	total

I think these are not particularly useful in the install-only distribution, and we could save some space. We skip shipping libpython.a but not these.