[scudo] Fix for the Scudo interface function scope

[cryptoad]

Summary

A forgotten include in scudo_allocator.cpp made the symbol only local :/

Before:

nm ./lib/clang/7.0.0/lib/linux/libclang_rt.scudo-i686-android.so | grep rss
00024730 t __scudo_set_rss_limit

After:

nm ./lib/clang/7.0.0/lib/linux/libclang_rt.scudo-i686-android.so | grep rs
00024760 T __scudo_set_rss_limit

And we want T!

This include also means that we can get rid of the extern "C" in the C++
file, the compiler does fine without it (note that this was already the case
for all the __sanitizer_* interface functions.

lib/scudo/scudo_allocator.cpp

 /// heap corruption vulnerabilities. It provides a checksum-guarded chunk
 /// header, a delayed free list, and additional sanity checks.
 ///
 //===----------------------------------------------------------------------===//
 
 #include "scudo_allocator.h"
 #include "scudo_crc32.h"
 #include "scudo_flags.h"
+#include "scudo_interface_internal.h"
 #include "scudo_tsd.h"
 #include "scudo_utils.h"
 
 #include "sanitizer_common/sanitizer_allocator_checks.h"
 #include "sanitizer_common/sanitizer_allocator_interface.h"
 #include "sanitizer_common/sanitizer_quarantine.h"
 
 #include <errno.h>

 }
 
 uptr __sanitizer_get_allocated_size(const void *Ptr) {
   return Instance.getUsableSize(Ptr);
 }
 
 // Interface functions
 
-extern "C" {
 void __scudo_set_rss_limit(uptr LimitMb, s32 HardLimit) {
   if (!SCUDO_CAN_USE_PUBLIC_INTERFACE)
     return;
   Instance.setRssLimit(LimitMb, !!HardLimit);
 }
-}  // extern "C"