allow caches to be disabled for memory-constrained environments
Submitted by Simon McVittie
Assigned to Simon McVittie
Related to Bug #33606, if the dbus-daemon's memory usage grows as a result of receiving messages faster than we can pass them on, it doesn't tend to deflate again.
On platforms where memory size is more important than throughput, it may be worthwhile to make various caches compile-time-configurable.