RFC: Support for unstable ABIs

[Simon Richter]

Hi,

a lot of projects that are just starting out still make quite a lot of
changes to their library ABI, so it does not make full sense to build a
shared library right away, but sometimes it is still necessary to have
PIC code around, for example when building a plugin to be dlopen()ed by
some program. If said library and the plugin code also live in separate
packages, you have a bit of a problem with current libtool.

The idea at this point would be to add another switch "-unstable-abi",
which would make libtool generate an archive instead of a shared library
(as it would for a convenience library), but also install both variants
(perhaps as libfoo.a and libfoo_pic.a). Shared object links against that
library would then simply include the ..._pic.a file on the linker
command line.

Comments?

   Simon