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

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",

libdl/libdl.cpp

@@ -23,11 +23,13 @@
 // These functions are exported by the loader
 // TODO(dimitry): replace these with reference to libc.so
 
+extern "C" {
+
 __attribute__((__weak__, visibility("default")))
 void* __loader_dlopen(const char* filename, int flags, const void* caller_addr);
 
 __attribute__((__weak__, visibility("default")))
-void* __loader_dlerror();
+char* __loader_dlerror();
 
 __attribute__((__weak__, visibility("default")))
 void* __loader_dlsym(void* handle, const char* symbol, const void* caller_addr);
@@ -212,3 +214,5 @@ __attribute__((__weak__))
 struct android_namespace_t* android_get_exported_namespace(const char* name) {
   return __loader_android_get_exported_namespace(name);
 }
+
+} // extern "C"