Add libuserdefs and use in cmd/{oamuser,passwd}

*** 221,230 ****
--- 221,231 ----
          libtnfprobe     \
          libtsnet        \
          libtsol         \
          libumem         \
          libunistat      \
+         libuserdefs     \
          libuuid         \
          libuutil        \
          libvolmgt       \
          libvrrpadm      \
          libvscan        \