- Fixes #11134

 - fixes #11125

- Don't duplicate the ret variable to err.
- Return -1 on any error, 0 otherwise.
- Set errno to return value of pthread_cond_timedwait.

The API of cond_timedwait was wrong. It used return -1 and set errno
instead of returning the error as specified for pthread_cond_timedwait
which it tries to mock.

Previous commit 98ae0186 changed the err variable to errno, which is not the return value we are looking for.

- fixes #11009

fix home position timestamp to be the timestamp that the home was set and not when the message was sent

zeroed uninitialized fields on home_position, mavlink_rc_channels_override, mavlink_mission_item, mavlink_mission_item_int

It turns out that `sendto` does not work for TCP on Cygwin-Windows,
instead we need to use `send`. This required some refactoring since we
need to have the internet protocol and the port stored as a member
variable.

This should fix that lockstep SITL simulation was not working on
Windows.

    - sitl_gazebo in PX4/Firmware (1f9b8333): https://github.com/PX4/sitl_gazebo/commit/c90e8ad2b27b95dc0b4c45b346509477c5fa593d
    - sitl_gazebo current upstream: https://github.com/PX4/sitl_gazebo/commit/e945745021a74ae45695a624dfc114a5c7bbd6bc
    - Changes: https://github.com/PX4/sitl_gazebo/compare/c90e8ad2b27b95dc0b4c45b346509477c5fa593d...e945745021a74ae45695a624dfc114a5c7bbd6bc

    e945745 2018-12-26 Julian Oes - worlds: fix rate for tailsitter and plane
46a3d27 2018-12-14 Jörg Schmidt - Fix bug in groundtruth altitude calculation

    - micro-CDR in PX4/Firmware (b043cfac5e8635d9017ad6a13f45795ad6fda6fb): https://github.com/eProsima/micro-CDR/commit/8b3546e8848e4c07c16ec55730d3ad1aa94396ab
    - micro-CDR current upstream: https://github.com/eProsima/micro-CDR/commit/7a76880f90dfe702f4fa1723e22d1dcb491d7b9e
    - Changes: https://github.com/eProsima/micro-CDR/compare/8b3546e8848e4c07c16ec55730d3ad1aa94396ab...7a76880f90dfe702f4fa1723e22d1dcb491d7b9e

    7a76880 2018-12-11 Julián Bermúdez Ortega - Badges (#24)

    - nuttx in PX4/Firmware (faf082fa1876b3f96ff9c07fc91ab8211d274c60): https://github.com/PX4/NuttX/commit/c225d4a691ef4572839b19635a84f2d9bf07ea74
    - nuttx current upstream: https://github.com/PX4/NuttX/commit/c225d4a691ef4572839b19635a84f2d9bf07ea74
    - Changes: https://github.com/PX4/NuttX/compare/c225d4a691ef4572839b19635a84f2d9bf07ea74...c225d4a691ef4572839b19635a84f2d9bf07ea74

- the flash-backend is selected by specifying nullptr as file or -1 as fd
- the default file is nullptr, and thus the FLASH
- 'param select' has no effect, FLASH is always the default

Thus there should be no functional change to existing setups.

Not all boards have an SD card.

This is a *breaking* change and requires a bootloader change.

Setting PWM_DISARMED to 0 results in no PWM output to the ESC for the pusher motor.
Most ESCs start beeping endless in short intervals if they don't get a signal.
I remove changing this parameter which is 900 by default to always command the motor to stand still.

Now that the lockstep changes are merged to master.

Now that this is merged to master in jMAVSim.