fuzz: add a script to build reproducers

fuzz: add a script to build reproducers

Currently, bash and C crash reproducers are be built manually. This is a
problem, as we want to integrate reproducers into the tree, for
regression testing. This patch adds a script that converts a sequence of
QTest commands into a pasteable Bash reproducer, or a libqtest-based C
program. This will try to wrap pasteable reproducers to 72 chars, but
the generated C code will not have nice formatting. Therefore, the C
output of this script should be piped through an auto-formatter, such as
clang-format

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>