databases/libmemcached: Fix build with -fno-common

Fix the build of databaes/libmemcached with -fno-common, which is the
default with llvm 11.

MFH:		2020Q3 (implicit, -fno-common fixes, ok by joenum)

databases/libmemcached/files/patch-clients_memaslap.c

@@ -0,0 +1,14 @@
+--- clients/memaslap.c.orig	2020-08-22 10:06:16 UTC
++++ clients/memaslap.c
+@@ -45,6 +45,11 @@
+ #define OPTIONSTRING const char*
+ #endif
+ 
++/* global variables */
++ms_global_t ms_global;
++ms_statistic_t ms_statistic;
++ms_stats_t ms_stats;
++
+ /* options */
+ static struct option long_options[]=
+ {

databases/libmemcached/files/patch-clients_ms__memslap.h

@@ -0,0 +1,23 @@
+--- clients/ms_memslap.h.orig	2020-08-22 10:06:28 UTC
++++ clients/ms_memslap.h
+@@ -116,14 +116,14 @@ typedef struct global
+   bool time_out;
+ } ms_global_t;
+ 
+-/* global structure */
+-ms_global_t ms_global;
++/* global structure, defined in memaslap.c */
++extern ms_global_t ms_global;
+ 
+-/* global stats information structure */
+-ms_stats_t ms_stats;
++/* global stats information structure, defined in memaslap.c */
++extern ms_stats_t ms_stats;
+ 
+-/* global statistic structure */
+-ms_statistic_t ms_statistic;
++/* global statistic structure, defined in mamaslap.c */
++extern ms_statistic_t ms_statistic;
+ 
+ #ifdef __cplusplus
+ }