Good news for users who can access S12. I've got a patch donated and now LibreOffice4 compiles the file "process.cxx" which before was failing on the now removed old header files "old_procfs.h".
The code now uses the regular procfs.h file on all Platforms. The procfs.h interfaces have been introduced with Solaris 2.6 and are deprecated since quite a number of years. With S12 the support for procfs.h has now ended.

Curently I'm recompiling boost in the new version 1.60.0 for S12 and if that succeeds, I'll rebuild those dependencies LibreOffice4 asks for and rely on boost.