parser: expand conditionals to allow comparisons

The apparmor parser supports if comparisons of boolean variables and
the definition status of set variables.

This commit expands the currently supported set to include comparisons
such as 'in', '>', '>=', '<', '<=', '==', and '!=' between
variables and/or text.

The comparison is done in lexicographical order, and since that can
cause issues comparing numbers, comparison between sets and numbers is
not allowed and the profile will fail to compile. Please refer to
apparmor.d.pod for example and details.

This commit also adds a file that generates test cases in the
parser. It is generated automatically with make check, but you can
generate them by running

make -C tst gen_conditionals

The generated tests will be under
tst/simple_tests/generated_conditional/

Signed-off-by: Georgia Garcia <georgia.garcia@canonical.com>

parser/variable.cc

@@ -66,8 +66,6 @@ char *variable::process_var(const char *var)
 		orig++;
 		len--;
 	} else {
-		PERROR("ASSERT: Found var '%s' without variable prefix\n",
-		       var);
 		return NULL;
 	}