Add meson build

This commit is to add meson build.
and later, we will remove Autotools and replace it with meson build.

Tested: built openpower-occ-control successfully and Unit test passes.

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: I7f5fbc7150194a78f9b36bb256613fc70b834130
diff --git a/gen/README b/gen/README
new file mode 100644
index 0000000..71182b5
--- /dev/null
+++ b/gen/README
@@ -0,0 +1,2 @@
+This directory contains generated meson.build files from sdbus++-gen-meson.
+Do not edit them by hand.