doc: Run language ref through prep.js

This is so we can strip out support code needed to make the examples work,
and as a bonus it does syntax highlighting.

doc/prep.js

@@ -40,7 +40,16 @@ var out = outfile ? fs.createWriteStream(outfile) : process.stdout;
 while ((line = lines[cur++]) != null) {
   if (/^~~~/.test(line)) {
     var block = "", bline;
-    var isRust = !/notrust/.test(line);
+    var notRust =
+          /notrust/.test(line)
+          // These are all used by the language ref to indicate things
+          // that are not Rust source code
+          || /ebnf/.test(line)
+          || /abnf/.test(line)
+          || /keyword/.test(line)
+          || /field/.test(line)
+          || /precedence/.test(line);
+    var isRust = !notRust;
     while ((bline = lines[cur++]) != null) {
       if (/^~~~/.test(bline)) break;
       if (!/^\s*##? /.test(bline)) block += bline + "\n";

mk/docs.mk

@@ -12,20 +12,25 @@ ifeq ($(CFG_PANDOC),)
   $(info cfg: no pandoc found, omitting doc/rust.pdf)
 else
 
+  ifeq ($(CFG_NODE),)
+    $(info cfg: no node found, omitting doc/tutorial.html)
+  else
+
 DOCS += doc/rust.html
 doc/rust.html: rust.md doc/version.md doc/keywords.md $(S)doc/rust.css
 	@$(call E, pandoc: $@)
-	$(Q)"$(CFG_PANDOC)" \
+	$(Q)$(CFG_NODE) $(S)doc/prep.js --highlight $< | \
+	"$(CFG_PANDOC)" \
          --standalone --toc \
          --section-divs \
          --number-sections \
          --from=markdown --to=html \
          --css=rust.css \
-         --output=$@ \
-         $<
+         --output=$@
 	@$(call E, cp: $(S)doc/rust.css)
 	-$(Q)cp -a $(S)doc/rust.css doc/rust.css 2> /dev/null
 
+  endif
 
   ifeq ($(CFG_PDFLATEX),)
     $(info cfg: no pdflatex found, omitting doc/rust.pdf)