Fix testcase.
Fix testcase.

The all-headers/distributed/tria_base.h.debug testcase failed because the
compiler is missing a forward declaration of parallel::Triangulation. Provide
this.

EGP-CIG-REU/dealii,angelrca/dealii,pesser/dealii,naliboff/dealii,ESeNonFossiIo/dealii,YongYang86/dealii,YongYang86/dealii,JaeryunYim/dealii,andreamola/dealii,JaeryunYim/dealii,ESeNonFossiIo/dealii,ESeNonFossiIo/dealii,sairajat/dealii,kalj/dealii,EGP-CIG-REU/dealii,johntfoster/dealii,johntfoster/dealii,shakirbsm/dealii,nicolacavallini/dealii,johntfoster/dealii,EGP-CIG-REU/dealii,kalj/dealii,Arezou-gh/dealii,JaeryunYim/dealii,danshapero/dealii,Arezou-gh/dealii,jperryhouts/dealii,danshapero/dealii,gpitton/dealii,danshapero/dealii,andreamola/dealii,ibkim11/dealii,EGP-CIG-REU/dealii,jperryhouts/dealii,shakirbsm/dealii,adamkosik/dealii,Arezou-gh/dealii,danshapero/dealii,Arezou-gh/dealii,angelrca/dealii,jperryhouts/dealii,angelrca/dealii,pesser/dealii,ESeNonFossiIo/dealii,sriharisundar/dealii,ibkim11/dealii,ESeNonFossiIo/dealii,naliboff/dealii,angelrca/dealii,sairajat/dealii,ibkim11/dealii,angelrca/dealii,sriharisundar/dealii,maieneuro/dealii,YongYang86/dealii,ibkim11/dealii,andreamola/dealii,gpitton/dealii,YongYang86/dealii,shakirbsm/dealii,ibkim11/dealii,maieneuro/dealii,sairajat/dealii,naliboff/dealii,nicolacavallini/dealii,gpitton/dealii,sriharisundar/dealii,nicolacavallini/dealii,shakirbsm/dealii,ibkim11/dealii,kalj/dealii,johntfoster/dealii,spco/dealii,jperryhouts/dealii,naliboff/dealii,maieneuro/dealii,andreamola/dealii,nicolacavallini/dealii,EGP-CIG-REU/dealii,spco/dealii,angelrca/dealii,andreamola/dealii,sairajat/dealii,shakirbsm/dealii,ibkim11/dealii,Arezou-gh/dealii,kalj/dealii,JaeryunYim/dealii,maieneuro/dealii,danshapero/dealii,YongYang86/dealii,adamkosik/dealii,YongYang86/dealii,pesser/dealii,JaeryunYim/dealii,spco/dealii,EGP-CIG-REU/dealii,sairajat/dealii,maieneuro/dealii,JaeryunYim/dealii,shakirbsm/dealii,Arezou-gh/dealii,pesser/dealii,kalj/dealii,nicolacavallini/dealii,gpitton/dealii,naliboff/dealii,jperryhouts/dealii,sriharisundar/dealii,nicolacavallini/dealii,adamkosik/dealii,sriharisundar/dealii,andreamola/dealii,naliboff/dealii,naliboff/dealii,maieneuro/dealii,JaeryunYim/dealii,EGP-CIG-REU/dealii,kalj/dealii,gpitton/dealii,Arezou-gh/dealii,johntfoster/dealii,kalj/dealii,spco/dealii,adamkosik/dealii,YongYang86/dealii,sriharisundar/dealii,adamkosik/dealii,angelrca/dealii,spco/dealii,pesser/dealii,sairajat/dealii,jperryhouts/dealii,gpitton/dealii,pesser/dealii,adamkosik/dealii,danshapero/dealii,danshapero/dealii,ESeNonFossiIo/dealii,johntfoster/dealii,sairajat/dealii,ESeNonFossiIo/dealii,adamkosik/dealii,spco/dealii,johntfoster/dealii,sriharisundar/dealii,nicolacavallini/dealii,shakirbsm/dealii,andreamola/dealii,gpitton/dealii,maieneuro/dealii,pesser/dealii,spco/dealii,jperryhouts/dealii