Resolve "Optimise renderer allocation for multichannel binaural rendering in external renderer"

• Related issues: #513 (closed)
• Requested reviewers: @sagnowski

Reason why this change is needed

Related to the TODO comment and subsequently commented lines in lib_rend.c::initMcBinauralRendering():

/* TODO tmu : needs review allocate both renderers; needed if headrotation is toggled so the renderer can be switched */

If headrotation is toggled then the renderer used may change (default is CREND, TD Object renderer is used for custom loudspeaker layouts or planar multichannel layouts with headrotation).

At the moment both renderers are always allocated, the possibly optimised solution here would be to allocate only the needed renderer, and if required close the other instance.

Description of the change

Additional logic was introduced to conditionally allocate and deallocate CREND and TD Object renderer handles depending on the rendering configuration.

Affected operating points

Affected: MC rendering in external renderer, expected full BE.