When starting HiTL, GCS set the home location, but did not identify it
as set=true. This patch fixes the behavior, as well as a minor variable
change to improve clarity.
Changed STANDARD_AIR_SEA_LEVEL_PRESSURE from KPa to Pa.
Added MIN, MAX, and sign macros to misc_math.h. The sign macro returns -1
for values less than 0, and 1 for values greater than or equal to 0. 0 is
specifically not handled different from strictly positive numbers.
Added library functions for computing atmospheric conditions.
Fixed hostile redefinition of bool.
Fixed simulation boolean defines.
Fixes from review.
Merge pull request #536 from kubark42/misc-fixes

Misc fixes