[libgtop] Provide stats about shared memory and account Slab as cached. This matches exactly `free`.

[Benoît Dejean <bdejean src gnome org>]

commit c33623c0978278932ea233ea0ca48c3d410cd5f2
Author: Benoît Dejean <bdejean gmail com>
Date:   Tue Jul 14 11:11:38 2015 +0200

    Provide stats about shared memory and account Slab as cached.
    This matches exactly `free`.

 sysdeps/linux/mem.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/sysdeps/linux/mem.c b/sysdeps/linux/mem.c
index 17f5193..e37a922 100644
--- a/sysdeps/linux/mem.c
+++ b/sysdeps/linux/mem.c
@@ -52,12 +52,13 @@ glibtop_get_mem_s (glibtop *server, glibtop_mem *buf)
 
        file_to_buffer(server, buffer, sizeof buffer, FILENAME);
 
+        /* try to match procps's `free` */
        buf->total  = get_scaled(buffer, "MemTotal:");
        buf->free   = get_scaled(buffer, "MemFree:");
        buf->used   = buf->total - buf->free;
-       buf->shared = 0;
+       buf->shared = get_scaled(buffer, "Shmem:");
        buf->buffer = get_scaled(buffer, "Buffers:");
-       buf->cached = get_scaled(buffer, "Cached:");
+       buf->cached = get_scaled(buffer, "Cached:") + get_scaled(buffer, "Slab:");
 
        if (server->os_version_code >= LINUX_VERSION_CODE(3, 14, 0)) {
                buf->user = buf->total - get_scaled(buffer, "MemAvailable:");