
Derived requirements on the build system plugin using gmake

B1) provide autoconf configure support.

B2) provide and manage all dependency information, so that 'make'
can be restarted at any point and end up with correct code.
Note: this constrains the python level (bocca core) to keep
impl files in sync with SIDL at all times.

B3) provide for the following invocations at the top level

make
make check
make install
make clean
make distclean

B4) provide user hooks (pre, post) actions around the B3 targets
to allow compile of external code on a per-component basis.

B5) allow dependency on external sidl files.

B6) allow the user to relax B2.
Note: typically this is done simply by using the editor
directly instead of via 'bocca edit'. When this occurs,
the only reentry to a dependency-tracked process is to
bocca edit --touch $symbol
