regcomp.c: Simplify /l Synthetic Start Class construction

regcomp.c: Simplify /l Synthetic Start Class construction

The ANYOF_POSIXL flag is needed in general for ANYOF nodes to indicate
if the struct contains an extra U32 element used to hold the list of
POSIX classes (like \w and [:punct:]) whose matches depend on the locale
in effect at the time of runtime pattern matching.

But the SSC always contains this U32, and so doesn't need to use the
flag.  Instead, if there aren't any such classes, the U32 will be zero.

Removing keeping track of this flag during the assembly of the SSC
simplifies things.  At the completion of this process, this flag is
set if the U32 is non-zero to pass that information on to regexec.c so
that it doesn't have to special case things.