EVIS: Remove strings from the stack

Keep a single string around and build it up incrementally. This avoids
string allocation within the stack which is much faster.
Help: Add documentation on escaping changes with CMP0053
Merge topic 'dev/faster-evis' into next

d720a7cb Help: Add documentation on escaping changes with CMP0053
d5174e3b EVIS: Remove strings from the stack