Revise whitespace and comment handling.

This makes whitespace significant by default, requiring (?x) to make it
insignificant again, as is the Perl 5 default. Also implements the (?#xxx)
comment syntax.

src/QRegex/P5Regex/Actions.nqp

@@ -232,7 +232,7 @@ class QRegex::P5Regex::Actions is HLL::Actions {
             make 0;
         }
     }
-   
+
     method p5mods($/) {
         for nqp::split('', ~$<on>) {
             %*RX{$_} := 1;
@@ -396,14 +396,6 @@ class QRegex::P5Regex::Actions is HLL::Actions {
 
     # XXX Below here copied from p6regex; needs review
 
-    method metachar:sym<ws>($/) {
-        my $qast := %*RX<s>
-                    ?? QAST::Regex.new(:rxtype<ws>, :subtype<method>, :node($/),
-                            QAST::Node.new( QAST::SVal.new( :value('ws') ) ))
-                    !! 0;
-        make $qast;
-    }
-
     method metachar:sym<'>($/) {
         my $quote := $<quote_EXPR>.ast;
         if QAST::SVal.ACCEPTS($quote) { $quote := $quote.value; }

src/QRegex/P5Regex/Grammar.nqp

@@ -121,7 +121,12 @@ grammar QRegex::P5Regex::Grammar is HLL::Grammar {
 
     token quantmod { [ '?' | '+' ]? }
 
-    token ws { [ \s+ | '#' \N* ]* }
+    token ws {
+        [
+        | '(?#' ~ ')' <-[)]>*
+        | <?{ %*RX<x> }> [ \s+ | '#' \N* ]
+        ]*
+    }
 
 
     # XXX Below here is straight from P6Regex and unreviewed.
@@ -141,7 +146,6 @@ grammar QRegex::P5Regex::Grammar is HLL::Grammar {
     rule arglist { <arg> [ ',' <arg>]* }
 
     proto token metachar { <...> }
-    token metachar:sym<ws> { <.normspace> }
     token metachar:sym<'> { <?[']> <quote_EXPR: ':q'> }
     token metachar:sym<"> { <?["]> <quote_EXPR: ':qq'> }
     token metachar:sym<lwb> { $<sym>=['<<'|'«'] }