[CLEAN\]DISCARD BufferName
Discard (i.e. remove from the memory and the list of known variables)
the specified buffer.
Only the most important buffers (e.g. DIRTY, CLEAN, etc...) can be dis-
carded. The current list is:
CCT, CLEAN, CONTINUUM, DIRTY, MASK, PRIMARY, RESIDUAL,
SINGLEDISH, SKY, UVCONT, UVSELF, UV_MODEL