This fixes the compiler warning with GCC 8.

in parameters.cpp

per @dagar: As soon as commander starts it runs the preflight checks which does the param_find.

This allows to use PX4 on systems that do not have a mag or a baro,
such as the Omnibus F4 SD.

Flight tested: ekf2 w/ mag and compass by @nathantsoi: https://logs.px4.io/plot_app?log=79b81031-cf1e-41f0-890b-d6cd7d559766

NOTE: external I2C devices need a pullup. I have tested with a 3.3v 2.2k pullup.

Working:
 - mpu6000, bench tested and verified via nsh
 - fmu
 - all 6 ch output bench tested w/ pwm and oneshot via nsh
 - ppm input bench tested
 - dsm input bench tested
 - bmp280, bench tested and verified via nsh
 - hmc5883, bench tested and verified via nsh, but requires an external i2c pullup
 - gps on uart6
 - startuplog, nsh, mavlink on uart4, but params are not sent for some reason. RSSI pin is TX, MOTOR 5 is RX (normal mode, 57600 baud)
 - rgbled over i2c, bench tested and workingp
 - sbus via the shared sbus/ppm pin (which includes an inverter to the mcu SBUS in pin), remove the solder bridge or jumper to the ppm pin before use

Not yet implemented:
  - ADC
  - OSD: passthrough video is untested, use at your own risk until a basic driver is implemented.

- fix start and end time indices calculation

PX4_ERR calls printf, which calls lib_sem_initialize, which calls sem_wait

avoids compile error on OSX, trying to cast pthread_t to pid_t

Helps debugging busy-looping tasks.

In case a log ends abruptly, we will know that we have everything up to the
last second.

A test showed that CPU load and the amount of logging drops are unaffected
by this.

This is to guard against busy-looping tasks, so that we at least have a
log. In case the watchdog is triggered, it also logs CPU load of all
tasks.

 * cb63f16 2018-05-17 Daniel Agar - cmake cache ECL source directory path to work with catkin (#447)
 * fixes #9447

Fixes #9451

Complete refactor of the lis3mdl driver. This has been bench tested, flight tested, and verified functional.

    - ecl in PX4/Firmware (bcebb33f8618c8d1827ae65b904e9d85f2610b52): https://github.com/PX4/ecl/commit/372f9f430bb0edb901b3265ecd0cddf8ee4d1ffb
    - ecl current upstream: https://github.com/PX4/ecl/commit/bae4b8a5e7786304e33deaf33bbbcbb256fdda1e
    - Changes: https://github.com/PX4/ecl/compare/372f9f430bb0edb901b3265ecd0cddf8ee4d1ffb...bae4b8a5e7786304e33deaf33bbbcbb256fdda1e

    bae4b8a 2018-05-11 Bart Slinger - remove superfluous elseif (#431)
16976d3 2018-05-11 Paul Riseborough - Merge branch 'pr-ekfOptFlowFixes'
75e6590 2018-05-10 Paul Riseborough - EKF: fix bug causing height offset when GPS use stops
e8e9e34 2018-05-10 Paul Riseborough - EKF: fix bug causing height offset when GPS use stops
6cadc92 2018-05-09 Paul Riseborough - EKF: Don't reject saturated flow data when it is the only aiding source
bf902e5 2018-05-09 Paul Riseborough - EKF: Prevent flow motion check false positives
bdf5b3e 2018-05-07 Paul Riseborough - EKF: Don't assume large position uncertainty when starting optical flow nav
e26711a 2018-05-05 Paul Riseborough - EKF: relax terrain update requirements for continuing optical flow use
868bc01 2018-05-05 Paul Riseborough - EKF: Relax minimum required range finder measurement rate
02963a8 2018-05-05 Paul Riseborough - EKF: relax optical flow on ground motion checks
24b005e 2018-05-03 Paul Riseborough - EKF: range finder aiding logic fixes
0c0a660 2018-05-03 Paul Riseborough - EKF: Decouple range finder use criteria checking and selection
6708bec 2018-04-29 Paul Riseborough - EKF: Don't auto select range finder for height when on ground.
0a63052 2018-04-26 Paul Riseborough - EKF: Fix false triggering of optical flow bad motion checks
f9d4934 2018-04-19 Paul Riseborough - EKF: update comments
82de314 2018-04-18 Paul Riseborough - EKF: Don't use optical flow if GPS is good and the vehicle is not using range finder for height
389786e 2018-03-12 Paul Riseborough - EKF: Stop using EV for yaw when GPS fusion starts
4ab7823 2018-02-26 Paul Riseborough - EKF: Add persistence criteria to  GPS fail check
67d71ca 2018-02-26 Paul Riseborough - EKF: allow GPS fallback if quality bad and alternative aiding available
bd59e38 2018-02-26 Paul Riseborough - EKF: always run GPS checks
b227aca 2018-05-05 Daniel Agar - geo_lookup fix table bounds
e494a4e 2018-05-05 Daniel Agar - Jenkins set git username and email with environment variables
3639087 2018-05-05 Daniel Agar - cmake and Jenkins add basic address santiizer test buld
1fba622 2018-05-05 Daniel Agar - travis-ci basic build script
cde2ee9 2018-05-05 Daniel Agar - cmake ignore missing-field-initializers
2100127 2018-05-05 Daniel Agar - geo: zeroing static unnecessary
0f12db5 2018-05-03 Daniel Agar - travis-ci enable coverity_scan
aceab8c 2018-05-05 Daniel Agar - Jenkins upload coverage to codecov.io
5780cd3 2018-05-05 Daniel Agar - Jenkins create PX4/Firmware test branch and push (#436)
cf957b5 2018-05-04 Daniel Agar - code coverage cmake and Jenkins support
4e0cd45 2018-05-03 Daniel Agar - doxygen cmake and Jenkins support

Reduces FLASH usage by about 3kb.

Plus add a missing cmake dependency.