Add a calloc self-test
Add a calloc self-test

Add a very basic test of calloc to the selftest program. The selftest
program acts in its capacity as a platform compatibility checker rather
than in its capacity as a test of the library.

The main objective is to report whether calloc returns NULL for a size
of 0. Also observe whether a free/alloc sequence returns the address
that was just freed and whether a size overflow is properly detected.

Mbed-TLS/mbedtls,ARMmbed/mbedtls,NXPmicro/mbedtls,Mbed-TLS/mbedtls,NXPmicro/mbedtls,NXPmicro/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,NXPmicro/mbedtls,ARMmbed/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls