Moved sim/ to test/simulator

All test code will be in test/. The simulator will be a subdirectory and
separate for all of the other unit test code.

Change-Id: I18c787c8180a93e09b91c74968284062391d915d
diff --git a/meson.build b/meson.build
index 802f682..7a569b6 100644
--- a/meson.build
+++ b/meson.build
@@ -6,10 +6,11 @@
             'cpp_std=c++11'
         ])
 
-incdir = include_directories('./')
+incdir = [ include_directories('src') ]
 
-build_simulator = get_option('tests')
+build_tests = get_option('tests')
 
-if not build_simulator.disabled()
-  subdir('sim')
+if not build_tests.disabled()
+  incdir += include_directories('test')
+  subdir('test')
 endif