BuildSystem: Cleanup userspace directory layout

userspace programs are now in userspace/programs
userspace tests are now in userspace/tests

This makes listing userspace projects much cleaner. Libraries were
already separated to their own directory, so other programs should also.

userspace/tests/test-mmap-shared/CMakeLists.txt

@@ -0,0 +1,8 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(test-mmap-shared ${SOURCES})
+banan_link_library(test-mmap-shared libc)
+
+install(TARGETS test-mmap-shared OPTIONAL)