create libosmo-mgcp and osmo-mgw by copying legacy code

This a cosmetic commit, copying libosmo-legacy-mgcp to libosmo-mgcp and
osmo-bsc_mgcp to osmo-mgw 1:1 at first, to provide a basis for next patches
that highlight the changes from legacy to new code.

Until osmo-msc and osmo-bsc are adjusted to operate with the new code, we will
keep the legacy code alongside the new code. The legacy code might be dropped
later.

Change-Id: Idf54481754a1765bdb2d0d7033bc0d7dc2018024
23 files changed