Shielding VCL Rendering, New VCL Syntax
Backend definitions with shielding enabled, and which use the 'shield' director, now have a simplified syntax that incorporates health checks, loop checks, and other checks in a single line of VCL.
Additionally, the minimum version of VCL available across our network increased, unlocking the following changes:
New variable
New function
Prior change: Regular expressions in VCL
Following change: VCL_RECV changes, x-compress-hint behavior change, bugfixes
