Factorise out bits of the other tests so that the code is cleaner and 
can be re-used.

cryptdlg: Add stubs for CertTrustInit, CertTrustCertPolicy, CertTrustCleanup and CertTrustFinalPolicy.

Support the static and register keywords.

This consolidates externdef and constdef rules into one declaration rule.

Return a decl_spec_t structure from decl_spec rules so that the storage
class and type qualifiers can both be returned.

widl: Make constdef and externdef take a declarator instead of an ident so that functions and arrays can be defined using the statements.