change ThirdParty-Xyz dependencies to Required

- works better with coinbrew's understanding of "optional"
- fixes coin-or/coinbrew#70

.coin-or/config.yml

@@ -22,15 +22,18 @@ Dependencies:
   - Description: ThirdParty wrapper for building ASL
     URL: https://github.com/coin-or-tools/ThirdParty-ASL
     Version: stable/2.0
-    Required: Optional
+    # actually optional, but then coinbrew would skip over it unless --enable-optional is set
+    Required: Required
   - Description: ThirdParty wrapper for building Mumps
     URL: https://github.com/coin-or-tools/ThirdParty-Mumps
     Version: stable/3.0
-    Required: Optional
+    # actually optional, but then coinbrew would skip over it unless --enable-optional is set
+    Required: Required
   - Description: ThirdParty wrapper for building HSL codes
     URL: https://github.com/coin-or-tools/ThirdParty-HSL
     Version: stable/2.2
-    Required: Optional
+    # actually optional, but then coinbrew would skip over it unless --enable-optional is set
+    Required: Required
   - Description: Parallel Sparse Direct Solver from Pardiso-Project
     URL: http://www.pardiso-project.org/
     Required: Optional