Safestring library with non-Linux environment

[divneil]

Hi Dave,

I am developing some solution on ARM Trustzone with OPTEE, so, would like to have safestring compile by default. There are 2 issues I am facing.

o errno.h: There's no errno.h file in optee_os
o ctype.h: to have the build find declaration of toupper().

Following are the PRs. Thanks for your review.
#34
#35

Regards,
Divneil