Added '-fno-delete-null-pointer-checks' to GCC compilation options

From Adam Green, regarding using -fno-delete-null-pointer-checks:

"I would argue that on Cortex-M processors, it is more dangerous to not
have it.  The compiler can actually generate incorrect code because it is
making an incorrect assumption (that reads from a NULL pointer will throw
an exception.)   The GCC for ARM developers should actually never enable
the delete-null-pointer-checks optimization for Cortex-M processors.
There is a comment in the GCC manual that indicates, "Some targets,
especially embedded ones, disable this option [delete-null-pointer-checks]
at all levels."  Not having this flag is pretty risky on the current
versions of GCC_ARM.  Just to clarify, this flag doesn't enable an
optimization...it disables an unsafe optimization."
Merge remote-tracking branch 'github/master'