compiler: Add Preprocessor Support

TODO: Test that file names are properly tracked in included
files.

Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Sources/Common/Support.swift

@@ -15,20 +15,6 @@
 // You should have received a copy of the GNU General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
-public struct SourceLocation: Equatable, CustomStringConvertible {
-  public let start: Int
-  public let extent: Int
-
-  public init(_ start: Int, _ extent: Int) {
-    self.start = start
-    self.extent = extent
-  }
-
-  public var description: String {
-    return "{\(self.start), \(self.extent)}"
-  }
-}
-
 public enum DebugLevel {
   case Trace
   case Verbose