On Posix platforms, the OS argument mechanism makes quoting/reparsing
unnecessary anyway, so this only affects Windows.
Add optional 'triggers' parameter to LLStringUtils::quote() (default: space
and double-quote). Only if the passed string contains a character in
'triggers' will it be double-quoted.
This is observed to fix a Windows-specific problem in which plugin child
process would fail to start because it wasn't expecting a quoted number.
Use LLStringUtils::quote() more consistently in LLProcess implementation for
logging.