Rename files and add some docs.

src/wren_common.h

@@ -0,0 +1,39 @@
+#ifndef wren_common_h
+#define wren_common_h
+
+// This header contains macros and defines used across the entire Wren
+// implementation. In particular, it contains "configuration" defines that
+// control how Wren works. Some of these are only used while hacking on
+// debugging Wren itself.
+//
+// This header is *not* intended to be included by code outside of Wren itself.
+
+// Define this to stress test the GC. It will perform a collection before every
+// allocation.
+//#define DEBUG_GC_STRESS
+
+// Define this to log memory operations.
+//#define TRACE_MEMORY
+
+#define NAN_TAGGING
+
+// If this is set, the VM's interpreter loop uses computed gotos. See this for
+// more: http://gcc.gnu.org/onlinedocs/gcc-3.1.1/gcc/Labels-as-Values.html
+// TODO(bob): Automatically define this based on whether or not it's supported.
+#define COMPUTED_GOTOS
+
+#ifdef DEBUG
+
+  #define ASSERT(condition, message)                                   \
+    if (!(condition)) {                                                \
+      printf("ASSERT FAIL " __FILE__ ":%d - %s\n", __LINE__, message); \
+      abort();                                                         \
+    }
+
+#else
+
+  #define ASSERT(condition, message) ;
+
+#endif
+
+#endif