syntax: implement support for ES6 template literals
      Implement support for ECMAScript 6 template literals which allow simple
interpolation of variable values into strings without resorting to
`sprintf()` or manual string concatenation.

treewide: move json-c compat shims into internal header file
      Do not expose the json-c compat functions in ucode's public headers to
avoid clashes when building on systems with modern json-c.

Also remove some explicit json-c/json-c.h includes in places where it is
not needed.

ci: debian: change path before attempting to invoke Git operations
      Fixes: dfaf05a ("ci: debian: automatically update changelog from Git tag")

Signed-off-by: Paul Spooren <mail@aparcar.org>