Don’t LEAVE_with_name("evalcomp") for syntax errors

Don’t LEAVE_with_name("evalcomp") for syntax errors

In S_doeval, if yystatus == 0 but there have been parser errors, then
there will be an extra scope on the scope stack inside the evalcomp
scope, causing an assertion failure with LEAVE_with_name("evalcomp").

This can happen with eval(q|""!=!~//|), which is a reduced version of
an eval in SNMP::Trapinfo’s test suite.

Under non-debugging builds, everything would have worked anyway,
as the LEAVE_with_name("evalcomp") would have left the scope
inside evalcomp.

Since POPBLOCK pops away the savestack markers on the scope stack, it
is not actually necessary to do LEAVE_with_name("evalcomp") at all
when there is a syntax error.