[os_crypto] update makefiles
[os_crypto] add const qualifiers and use explicit os_md5 and os_sha1 instead of char *
[os_crypto] fix CID 28438
[os_crypto] fix sign compare
[os_crypto] fix CID 28439
[os_crypto] make ErrorExit() as noreturn, for static analysers
[os_crypto] add nonnull attributes where suiteable
[os_crypto] fix sign warnings
[os_crypto] uncomment unnecessary variable cleaning (is cleaned later on)
[os_crypto] reduce variable scope and indent branched code
[os_crypto] use snprintf instead of 3 other string operations
[os_crypto] avoid make -C due to bsd compatibility
[os_crypto] make some casts explicit
[os_crypto] fix some conversion warnings and reduce scope of global variables
[os_crypto] check snprintf call
Merge pull request #240 from cgzones/os_crypto

Some cosmetic and security related changes in os_crypto.