Restructure header files.

This should prevent the tests from being recompiled.

2019/src/day01.cpp

@@ -2,7 +2,7 @@
 #include <iterator>
 #include <vector>
 #include <unordered_set>
-#include "solutions.hpp"
+#include "days.hpp"
 
 // Currently an implementation of 2018 day 1
 void aoc2019::day01_part1(std::istream &input, std::ostream &output) {

2019/src/days.hpp

@@ -3,10 +3,6 @@
 #include <iosfwd>
 
 namespace aoc2019 {
-    typedef void (*solution_t)(std::istream &, std::ostream &);
-
-    solution_t get_implementation(int day, bool part2 = false);
-
     // Declarations of all implemented days.
     void day01_part1(std::istream &input, std::ostream &output);
     void day01_part2(std::istream &input, std::ostream &output);

2019/src/implementations.cpp

@@ -1,5 +1,6 @@
 #include <array>
-#include "solutions.hpp"
+#include "days.hpp"
+#include "implementations.hpp"
 
 constexpr const std::array<std::array<aoc2019::solution_t, 2>, 25> SOLUTIONS = {
         {aoc2019::day01_part1, aoc2019::day01_part2}

2019/src/implementations.hpp

@@ -0,0 +1,9 @@
+#pragma once
+
+#include <iosfwd>
+
+namespace aoc2019 {
+    typedef void (*solution_t)(std::istream &, std::ostream &);
+
+    solution_t get_implementation(int day, bool part2 = false);
+}

2019/src/runner.cpp

@@ -1,4 +1,4 @@
-#include "solutions.hpp"
+#include "implementations.hpp"
 #include <chrono>
 #include <iostream>
 #include <boost/program_options.hpp>