davfs2: fix compilation with GCC10

Signed-off-by: Rosen Penev <rosenp@gmail.com>

net/davfs2/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=davfs2
 PKG_VERSION:=1.5.5
-PKG_RELEASE:=2
+PKG_RELEASE:=3
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=@SAVANNAH/davfs2

net/davfs2/patches/400-gcc10.patch

@@ -0,0 +1,11 @@
+--- a/src/dav_coda.c
++++ b/src/dav_coda.c
+@@ -97,7 +97,7 @@ static unsigned int blocksize;
+ static size_t alignment;
+ 
+ /* Send debug messages to syslog if != 0. */
+-int debug;
++extern int debug;
+ 
+ 
+ /* Private function prototypes */