RFR (S): 8140343: SEGV in DirectivesStack::getMatchingDirective

[Nils Eliasson]

Hi all,

This fixes a bug when using a compiler that doesn't have compiler 
directives. This is a temporary fix using the default directive for c1. 
In the future permanent fix all compilers will have directives by default.

bug: https://bugs.openjdk.java.net/browse/JDK-8140343
webrev: http://cr.openjdk.java.net/~neliasso/8140343/webrev.01/

Please review,
Nils