Clean up the 32-bit kernel support, fix LP64 fcntl declaration.

In practice, thanks to all the registers the stubs don't actually change,
but it's confusing to have an incorrect declaration.

I suspect that fcntl remains broken for aarch64; it happens to work for
x86_64 because the first vararg argument gets placed in the right register
anyway, but I have no reason to believe that's true for aarch64.

This patch adds a unit test, though, so we'll be able to tell when we get
as far as running the unit tests.

Change-Id: I58dd0054fe99d7d51d04c22781d8965dff1afbf3
diff --git a/tests/Android.mk b/tests/Android.mk
index 3345e3e..ca6a06b 100644
--- a/tests/Android.mk
+++ b/tests/Android.mk
@@ -60,6 +60,7 @@
 test_src_files = \
     dirent_test.cpp \
     eventfd_test.cpp \
+    fcntl_test.cpp \
     fenv_test.cpp \
     getauxval_test.cpp \
     getcwd_test.cpp \