- Add strmov_overlapp.c where it's needed
- Add libevent where it is required
- Fix typo in unittest/mysys/waiting_threads-t.c
- fix xtradb C language source so that they have variable declarations before
  any operators, as it is (or was?) required in C.

libmysql/CMakeLists.txt:
  - Add strmov_overlapp.c where it's needed
sql/CMakeLists.txt:
  - Add strmov_overlapp.c where it's needed
  - Add libevent where it is required
storage/xtradb/btr/btr0cur.c:
  - fix xtradb C language source so that they have variable declarations before
    any operators, as it is (or was?) required in C.
storage/xtradb/buf/buf0buddy.c:
  - fix xtradb C language source so that they have variable declarations before
    any operators, as it is (or was?) required in C.
storage/xtradb/buf/buf0flu.c:
  - fix xtradb C language source so that they have variable declarations before
    any operators, as it is (or was?) required in C.
storage/xtradb/fil/fil0fil.c:
  - fix xtradb C language source so that they have variable declarations before
    any operators, as it is (or was?) required in C.
storage/xtradb/handler/i_s.cc:
  - fix xtradb C language source so that they have variable declarations before
    any operators, as it is (or was?) required in C.
storage/xtradb/srv/srv0srv.c:
  - fix xtradb C language source so that they have variable declarations before
    any operators, as it is (or was?) required in C.
strings/CMakeLists.txt:
  - Add strmov_overlapp.c where it's needed
unittest/mysys/waiting_threads-t.c:
  - Fix typo in unittest/mysys/waiting_threads-t.c