apinger: fix compilation with GCC 10

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

net/apinger/Makefile

@@ -10,7 +10,7 @@ include $(TOPDIR)/rules.mk
 PKG_NAME:=apinger
 PKG_SOURCE_DATE:=2015-04-09
 PKG_SOURCE_VERSION:=78eb328721ba1a10571c19df95acddcb5f0c17c8
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL:=https://github.com/Jajcus/apinger

net/apinger/patches/020-gcc10.patch

@@ -0,0 +1,11 @@
+--- a/src/apinger.h
++++ b/src/apinger.h
+@@ -111,7 +111,7 @@ struct piped_info {
+ };
+ #endif
+ 
+-struct target *targets;
++extern struct target *targets;
+ 
+ extern int foreground;
+ extern char *config_file;