Regenerate PDFs. Also fix a Makefile problem: protocol.pdf can't be a symlink

because GitHub doesn't follow symlinks, so links to protocol.pdf would break.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>

protocol/Makefile

@@ -37,7 +37,7 @@ auxsapling:
 sapling:
 	$(MAKE) auxsapling
 	mv -f aux/sapling.pdf .
-	ln -sf sapling.pdf protocol.pdf
+	cp -f sapling.pdf protocol.pdf
 
 .PHONY: pvcsapling
 pvcsapling:
@@ -107,7 +107,7 @@ optsapling: optimizer-installed.flag
 	$(MAKE) auxsapling
 	PATH="${PATH}:$(CURDIR)/sam2p:$(CURDIR)/tif22pnm" pdfsizeopt/pdfsizeopt --v=40 --use-image-optimizer=sam2p \
               --tmp-dir=aux aux/sapling.pdf sapling.pdf
-	ln -sf sapling.pdf protocol.pdf
+	cp -f sapling.pdf protocol.pdf
 
 .PHONY: optimized
 optimized: optsprout optsapling

protocol/protocol.ver

@@ -1,2 +1,2 @@
 \toggletrue{issapling}
-\renewcommand{\docversion}{Version 2018.0-beta-23 [\SaplingSpec]}
+\renewcommand{\docversion}{Version 2018.0-beta-25 [\SaplingSpec]}