Big number itself does not make much sense in some cases. Format the
bitshift format as well.

Changes our web page docs from:

VIR_MIGRATE_POSTCOPY = 32768 : Setting the VIR_MIGRATE_POSTCOPY...
VIR_MIGRATE_TLS      = 65536 : Setting the VIR_MIGRATE_TLS flag...

to:

VIR_MIGRATE_POSTCOPY = 32768 (0x8000; 1 << 15)  : Setting the VIR_MIGRATE_POSTCOPY...
VIR_MIGRATE_TLS      = 65536 (0x10000; 1 << 16) : Setting the VIR_MIGRATE_TLS flag...
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>