opennds: [21.02] Backport of Release v9.2.0

opennds: [21.02] Backport of Release v9.2.0

Maintainer: Rob White rob@blue-wave.net
Compile tested: arm_cortex-a7_neon-vfpv4, mipsel_24kc
Run tested: arm_cortex-a7_neon-vfpv4, mipsel_24kc, gl-inet b1300, gl-inet mt300n-v2, Snapshot, 21.02.0-rc3, 19.07.7

Description:
This version adds new functionality, improves performance, adds documentation and fixes an issue
  * Add - new config options to ndsctl status [bluewave.net]
  * Add - Readthedocs / man documentation for configuration options [bluewave.net]
  * Add - Faster convergence of average rates to configured rate quotas [bluewave.net]
  * Add - BinAuth parse authenticated client database for client data [bluewave.net]
  * Add - Use heap allocation for http page buffer allowing large page sizes [bluewave.net]
  * Fix - fail to serve downloaded images on custom themespec [bluewave.net]

Signed-off-by: Rob White <rob@blue-wave.net>