Add softrandommap and --alloc-size options

The softrandommap job option allows fio to continue if it cannot
allocate from the smalloc backing for the random map. Or the user
can specify --alloc-size with a size larger than the default of 1024k
to increase the size of the shared allocation pool.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/smalloc.h b/smalloc.h
index d5d4557..6905c6a 100644
--- a/smalloc.h
+++ b/smalloc.h
@@ -7,4 +7,6 @@
 extern void sinit(void);
 extern void scleanup(void);
 
+extern unsigned int smalloc_pool_size;
+
 #endif