They caused stack usage increase with -fstrict-aliasing as stack slots are not reused when dealing with unions.
It has now been added the cast_struct_to_array macro in pios_struct_helper.h to handle such case where it is useful to access those homogeneous structs as arrays
+review OPReview-552
Also fixes warnings (and bugs) in F4 STM32_USB_OTG_Driver code, allowing -Werror to be enabled for all flight code.
Fixes all other compiler warnings that would otherwise cause the flight code to not compile with -Werror enabled.
Along the way, this also adds some uses of isnan() to various places rather than questionable tests for x != x and
x == x to check for NaNs.
+review OPReview
