Update the results for step-18.
Update the results for step-18.

This commit updates the discussion (we no longer have to rewrite
makefiles), the timing values (happily, the program runs about 20x
faster now than when these results were recorded at some point in the
past, which most likely in 2002-2005 based on the mention of the
Athlon XP processor), and the output files from the simulation.

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