neofetch: Use MemAvailable for memory on Linux if supported. Closes d…

…ylanaraps#1591

neofetch

@@ -2568,10 +2568,21 @@ get_memory() {
                     "MemFree" | "Buffers" | "Cached" | "SReclaimable")
                         mem_used="$((mem_used-=${b/kB}))"
                     ;;
+
+                    # Available since Linux 3.14rc (34e431b0ae398fc54ea69ff85ec700722c9da773).
+                    # If detected this will be used over the above calculation for mem_used.
+                    "MemAvailable")
+                        mem_avail=${b/kB}
+                    ;;
                 esac
             done < /proc/meminfo
 
-            mem_used="$((mem_used / 1024))"
+            if [[ $mem_avail ]]; then
+                mem_used=$(((mem_total - mem_avail) / 1024))
+            else
+                mem_used="$((mem_used / 1024))"
+            fi
+
             mem_total="$((mem_total / 1024))"
         ;;