Merge pull request open-mpi#1164 from ggouaillardet/topic/v2.x/memory_patcher_common_symbol

memory/patcher: declare __curbrk as extern in order not to generate a…

Author: jsquyres

opal/mca/memory/patcher/memory_patcher_component.c

@@ -247,7 +247,7 @@ static int intercept_madvise (void *start, size_t length, int advice)
 #if defined SYS_brk
 
 #if OPAL_MEMORY_PATCHER_HAVE___CURBRK
-void *__curbrk; /* in libc */
+extern void *__curbrk; /* in libc */
 #endif
 
 static int (*original_brk) (void *);