Fix for -fno-common

Index: pimd/pim_version.h
--- pimd/pim_version.h.orig
+++ pimd/pim_version.h
@@ -25,6 +25,6 @@
 
 #define PIMD_VERSION_STR "0.166"
 
-const char * const PIMD_VERSION;
+extern const char * const PIMD_VERSION;
 
 #endif /* PIM_VERSION_H */