unittest,memory: Fix tests

src/nvim/memory.h

@@ -1,6 +1,7 @@
 #ifndef NVIM_MEMORY_H
 #define NVIM_MEMORY_H
 
+#include <stdbool.h>  // for bool
 #include <stdint.h>  // for uint8_t
 #include <stddef.h>  // for size_t
 #include <time.h>  // for time_t

test/unit/preprocess.lua

@@ -123,6 +123,7 @@ function Gcc:init_defines()
   self:define('INIT', {'...'}, '')
   self:define('_GNU_SOURCE')
   self:define('INCLUDE_GENERATED_DECLARATIONS')
+  self:define('UNIT_TESTING')
   -- Needed for FreeBSD
   self:define('_Thread_local', nil, '')
   -- Needed for macOS Sierra