Add log_displayer support for -m and -p.

These options work as advertised in the help message. Also add
a new function in util for converting strings to numbers.

Change-Id: I33ab9add3f55c9139557b30ffe4de633782933e5
diff --git a/aos/common/util/util.gyp b/aos/common/util/util.gyp
index fa1fb7f..5008dd8 100644
--- a/aos/common/util/util.gyp
+++ b/aos/common/util/util.gyp
@@ -70,6 +70,24 @@
       ],
     },
     {
+      'target_name': 'string_to_num',
+      'type': 'static_library',
+      'sources': [
+        #'string_to_num.h',
+      ],
+    },
+    {
+      'target_name': 'string_to_num_test',
+      'type': 'executable',
+      'sources': [
+        'string_to_num_test.cc',
+      ],
+      'dependencies': [
+        ':string_to_num',
+        '<(EXTERNALS):gtest',
+      ],
+    },
+    {
       'target_name': 'thread',
       'type': 'static_library',
       'sources': [