Rename libdl.c to libdl.cpp.

The no-arg function definitions in libdl.c weren't strictly correct,
because they should have taken void. Rename .c to .cpp instead of
fixing them.

Test: mma
Change-Id: I9e3528c836ffc8625a6a4d529034263b19b9fb3a
diff --git a/libdl/Android.bp b/libdl/Android.bp
index b0bbe99..44daaec 100644
--- a/libdl/Android.bp
+++ b/libdl/Android.bp
@@ -4,7 +4,7 @@
 cc_library_static {
     name: "libdl_static",
 
-    srcs: ["libdl.c", "libdl_cfi.cpp"],
+    srcs: ["libdl.cpp", "libdl_cfi.cpp"],
 
     cflags: [
         "-Wall",