361901 - p2 metadata of org.eclipse.swt is incomplete

Ensure installation of fragments of org.eclipse.swt
- Make sure that SWT can be installed with p2: whenever the bundle
  org.eclipse.swt is installed, the appropriate native fragment
  shall be installed as well. This is achieved by adding
  install-time dependencies, filtered by the running platform, from
  org.eclipse.swt to all its fragments.
- The install-time dependencies are disabled at build time because
  otherwise there would be a circular dependency between the host
  and its fragments. This is achieved through the additional
  condition "(!(org.eclipse.swt.buildtime=true))" in the filters
  which is made evaluate to false by setting
  org.eclipse.swt.buildtime=true in the build.
- Modified buildSWT.xml to generate the time-stamp qualifiers and write
the qualifiers in the pom files in source and binaries repos.

Bug: 361901
Change-Id: I37b1f6c0ea5231850319e1fc4098e412e327d7e2
Signed-off-by: Tobias Oberlies <tobias.oberlies@sap.com>
Signed-off-by: Lakshmi Shanmugam <lshanmug@in.ibm.com>