v5.2.1

Paparazzi 5.2.1_stable

Maintenance release

• build system: remove 'load' target as it is a builtin directive in Make 4.0
• fix FlightGear visualization on 32bit systems
• flight plans: set primitive should not delay next stage
  #824
• flight plans: fix return primitive
• generators: gen_airframe: don't force float if unit = code_unit
• sys_time: up to 16 sys_time timers by default (was 8)
• OCaml: fix Pprz.sprint_value for uint32, e.g. for NatNet
  #831
• Rotorcraft: auto-enable UNLOCKED_HOME_MODE if HOME mode is used on RC
  #823
• Rotorcraft: only go to HOME mode if in NAV
  #850
• Fixedwing: If USE_BARO_BOARD: separate baro timer
  Before baro_periodic was running at PERIODIC_FREQUENCY in sensors_task,
  which is too fast for ms5611 if periodic freq is > 100Hz.
• INS alt_float: if USE_BARO_BOARD, dt is 1/BARO_PERIODIC_FREQUENCY
  #848
• STM32: backport fix for using multiple ADs
  #822
• LPC21: don't override T0CCR values when setting ppm and trig_ext
• IMU driver for Lisa/M/MX 2.1
  #817
• support for HBmini board
  #864