The source file libroot_stubs.c contains empty stubs for all symbols exported by
libroot.so, including definitions of all versioned symbols.

From libroot_stubs.c, <stubbed>libroot.so can be built, which is a stubbed
version of libroot.so (i.e. without any code). This stubbed library is used
during stage 0 of the bootstrap process, in order to build the gcc-syslibs
(libgcc, libsupc++ and libstdc++).

The python script generate_stubs.py can be used to regenerate libroot_stubs.c
from a built version of (the real) libroot.so. This may be necessary when new
symbols have been added to libroot.so.

The command for regenerating libroot_stubs.c is this:

	nm <path-to-libroot.so> | generate_stubs.py >libroot.stubs.c

There is a separate version of the stubs file for the legacy compiler (gcc2),
which uses a different symbol mangling format and contains the symbols for
libgcc, too.