Fix builds of net/samba46 and net/samba47 when using lld 7.0.0.

With lld 7.0.0, the following error is emitted:

ld: error: duplicate symbol 'pdb_search_init' in version script

This is because the symbol version scripts generated by wscript_build
contain both "pdb_search_init" in the global section, and "pdb_*_init"
in the local section. Fix it by removing "pdb_*_init" from the local
section.

For net/samba48, this already got fixed, as a side effect of r478825.

Approved by: portmgr (antoine)
PR: 230602
MFH: 2018Q4