i#1542: handle double quotes in client options

Augments drconfiglib to pick a -client_lib delimiter to avoid quote
character conflicts.

Adds DR_CONFIG_OPTIONS_INVALID, with drconfiglib returning it when it finds
; or can't find a delimiter (== client path + options together contain all
3 quote types).

Documents these limitations in intro.dox and dr_config.h.

Fixes issue 1542

SVN-Revision: 2835
4 files changed