Consolidate build instructions and troubleshooting into WSDG chapter 2.
Remove (moved) troubleshooting note that libpcap is required.
Link from WSUG build instructions to the WSDG chapters.
Reorder WSUG to have install instructions before build instructions for both
Windows and Unix.
Link from WSDG build instructions in WSDG sources chapter back to
WSDG chapter 2.
Offer options to the 'git clone' lines in obtaining sources: '--depth' and
'--shallow-since'
Add brief descriptions of new options mentioned.