Include system RAM size in usage report

cmd/syncthing/memsize_linux.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func memorySize() (uint64, error) {
+	f, err := os.Open("/proc/meminfo")
+	if err != nil {
+		return 0, err
+	}
+
+	s := bufio.NewScanner(f)
+	if !s.Scan() {
+		return 0, errors.New("/proc/meminfo parse error 1")
+	}
+
+	l := s.Text()
+	fs := strings.Fields(l)
+	if len(fs) != 3 || fs[2] != "kB" {
+		return 0, errors.New("/proc/meminfo parse error 2")
+	}
+
+	kb, err := strconv.ParseUint(fs[1], 10, 64)
+	if err != nil {
+		return 0, err
+	}
+	return kb * 1024, nil
+}