scripts: emit raw enum value in API build description

scripts: emit raw enum value in API build description

Currently the value for an enum is only emitted if it is a plain
string. If the enum is an integer or hex value, or a complex code block,
it is omitted from the API build. This fixes that by emitting the raw
value if no string value is present.

With this change:

  <macro name='LIBVIR_CHECK_VERSION'
         file='libvirt-common'
         params='major,minor,micro'>
  <macro name='LIBVIR_VERSION_NUMBER'
         file='libvirt-common'>
  <macro name='VIR_COPY_CPUMAP'
         file='libvirt-domain'
         params='cpumaps,maplen,vcpu,cpumap'>
  ...snip...

  <macro name='LIBVIR_CHECK_VERSION'
         file='libvirt-common'
         params='major,minor,micro'
         raw='((major) * 1000000 + (minor) * 1000 + (micro) <= LIBVIR_VERSION_NUMBER)'>
  <macro name='LIBVIR_VERSION_NUMBER'
         file='libvirt-common'
         raw='6004000'>
  <macro name='VIR_COPY_CPUMAP'
         file='libvirt-domain'
         params='cpumaps,maplen,vcpu,cpumap'
         raw='memcpy(cpumap, VIR_GET_CPUMAP(cpumaps, maplen, vcpu), maplen)'>
  ...snip...

Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>