[lldb/API] Use std::make_unique<> (NFC)

I was holding off on this change until we moved to C++14 as to not have
to convert llvm::make_unique to std::make_unique. That happened a while
ago so here's the first patch for the API which had a bunch of raw
`new`s.

lldb/source/API/SBProcessInfo.cpp

@@ -39,7 +39,7 @@ SBProcessInfo &SBProcessInfo::operator=(const SBProcessInfo &rhs) {
 
 ProcessInstanceInfo &SBProcessInfo::ref() {
   if (m_opaque_up == nullptr) {
-    m_opaque_up.reset(new ProcessInstanceInfo());
+    m_opaque_up = std::make_unique<ProcessInstanceInfo>();
   }
   return *m_opaque_up;
 }