Add android_dlopen_ext() interface to linker.

Add a function "android_dlopen_ext()", defined in <android/dlext.h>.
This is an extended version of dlopen() which takes a struct for passing
additional parameters for Android-specific functionality. This will be
used to support RELRO section sharing between separate processes.

Bug: 13005501
Change-Id: I9c99b2f2a02ee329dedaeba09ef3a1113b17b2d6
diff --git a/linker/linker.h b/linker/linker.h
index b8d0587..93ab51d 100644
--- a/linker/linker.h
+++ b/linker/linker.h
@@ -32,6 +32,7 @@
 #include <elf.h>
 #include <link.h>
 #include <unistd.h>
+#include <android/dlext.h>
 
 #include "private/libc_logging.h"
 
@@ -192,7 +193,7 @@
 
 void do_android_get_LD_LIBRARY_PATH(char*, size_t);
 void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path);
-soinfo* do_dlopen(const char* name, int flags);
+soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo);
 int do_dlclose(soinfo* si);
 
 ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start);