Merge branch 'tzlatinski_memory_allocaiton_size_fix' into 'master'

CTS Memory tests fix invalid allocation sizes

allocateRandom() routine sometime requests enormous sizes
because of incorrect random size calculation logic.

Within the following formula:
m_heap.size / MAX_MEMORY_USAGE_DIV) - m_usage - 1ull
If m_heap.size / MAX_MEMORY_USAGE_DIV) - m_usage is "0"
the result is negative, but since the number is unsigned
max takes the max of 1 and the (unsigned long long)-1.

The change, makes the comparison signed and also introduces
explicit test checks on the allocation sizes.

See merge request !389