topics: add memory management
topics: add memory management

Saw this in the c track, not as common anymore because of garbage
collection but still a worthy addition for some problems with large
data sets.

ErikSchierboom/x-common,petertseng/x-common,rpottsoh/x-common,Vankog/problem-specifications,jmluy/x-common,jmluy/x-common,petertseng/x-common,rpottsoh/x-common,exercism/x-common,Vankog/problem-specifications,ErikSchierboom/x-common,exercism/x-common,jmluy/x-common