restored two writer threads after finding/fixing unrelated bug

src/camogm.h

@@ -30,7 +30,7 @@
 #include <syslog.h>
 #include <malloc.h> // debugging
 
-#define NUM_WRITER_THREADS        1+0 // 2
+#define NUM_WRITER_THREADS        2 // 1+0 // 2
 
 #define NUM_NEED_EMPTY            (NUM_WRITER_THREADS + 1) // run main thread to prepage more pages if >= empty
 #define NUM_NEED_NEMPTY           (NUM_WRITER_THREADS + 0) // wake up main thread if there are at least this number of empty pages