bugfix! libc wrapping always segfaulted in init_libc_iface

libc wrapping uses table_dlsym to find libc entry points, and a previous
commit added a BUG() statement on table_dlsym failure. We don't want
that failure in init_libc_iface - we expect some symbols not to be
there. This patch adds a parameter to the table_dlsym to switch between
the different functionality.

Signed-off-by: Jeremy C. Andrus <jeremya@cs.columbia.edu>
add library name to logfile name

This will allow multiple libraries to be wrapped and logging
simultaneously without stepping on each other's toes.

Signed-off-by: Jeremy C. Andrus <jeremya@cs.columbia.edu>
Initial Java backtracing framework (incomplete)

This is a state-saving commit that presents the basic java backtracing
interface. The functions don't do anything interesting yet, but the
libdvm functions have been discovered, and the basic mechanismis in
place.

Signed-off-by: Jeremy C. Andrus <jeremya@cs.columbia.edu>