Custom warning messages for permissions are appended to the default security warning

A custom warning message defined by the warning property in a permission definition is now appended to the default security warning displayed when the permission has restrict access set to true. Previously, setting a custom warning message in this way would override the default warning altogether.

Before
Permission with no custom warning message:

insert javascript:
  title: 'Insert custom JavaScript into pages'
  restrict access: true

Warning displayed:

Warning: Give to trusted roles only; this permission has security implications.

Permission with custom warning message:

insert javascript:
  title: 'Insert custom JavaScript into pages'
  restrict access: true
  warning: 'This permission is dangerous because it allows injecting arbitrary JS.'

Warning displayed:

This permission is dangerous because it allows injecting arbitrary JS.

After
Permission with custom warning message:

insert javascript:
  title: 'Insert custom JavaScript into pages'
  restrict access: true
  warning: 'This permission is dangerous because it allows injecting arbitrary JS.'

Warning displayed:

Warning: Give to trusted roles only; this permission has security implications. This permission is dangerous because it allows injecting arbitrary JS.