lib: add a version string

Signed-off-by: Zygo Blaxell <bees@furryterror.org>

include/crucible/version.h

@@ -0,0 +1,8 @@
+#ifndef CRUCIBLE_VERSION_H
+#define CRUCIBLE_VERSION_H
+
+namespace crucible {
+	extern const char *VERSION;
+}
+
+#endif CRUCIBLE_VERSION_H