cosmetic: rename SL3_TXT macro, use osmo_strlcpy()

Rename SL3_TXT to more accurate copy_sqlite3_text_to_buf(), and use
osmo_strlcpy() instead of essentially dup'ing it.

The macro will also be used by hlr_db_tool.c in upcoming patch. This patch
prepares for a move to db.h.

Change-Id: I1dadeddddcfe0109195c09c0e706201b0df009cc
1 file changed