More improvements to the new memory manager

the memory manager now compiles with g++4.7. The hugepages example
now shows how the memory monitor is used.

examples/hugepages.cpp

@@ -16,7 +16,7 @@ void do_something(const tCsa& csa)
         sum+=csa.psi(i);
     }
     auto stop = timer::now();
-    cout << "runtime in ms: " << duration_cast<microseconds>(stop-start).count() << endl;
+    cout << "runtime in s: " << duration_cast<seconds>(stop-start).count() << endl;
     cout <<"sum="<<sum<<endl;
 }
 
@@ -33,10 +33,18 @@ int main(int argc, char** argv)
         memory_manager::use_hugepages(500*1024*1024);
     }
 
+    memory_monitor::start();
+
     csa_wt<> csa;
     auto start = timer::now();
     construct(csa, argv[1], 1);
     auto stop = timer::now();
-    cout << "construction in ms: " << duration_cast<microseconds>(stop-start).count() << endl;
+    cout << "construction in s: " << duration_cast<seconds>(stop-start).count() << endl;
     do_something(csa); // before it is mapped
+
+    memory_monitor::stop();
+
+    std::ofstream ofs("cst-construction.json");
+    memory_monitor::write_memory_log<JSON>(ofs);
+    ofs.close();
 }

include/sdsl/memory_management.hpp

@@ -36,7 +36,7 @@ class memory_monitor
             int64_t usage;
             mm_event(timer::time_point t,int64_t u) : timestamp(t) , usage(u) {};
         };
-        std::chrono::milliseconds log_granularity = std::chrono::milliseconds(50);
+        std::chrono::milliseconds log_granularity = std::chrono::milliseconds(20);
         int64_t current_usage = 0;
         int64_t peak_usage = 0;
         bool track_usage = false;

lib/memory_management.cpp

@@ -290,7 +290,7 @@ hugepage_allocator::remove_from_free_set(mm_block_t* block)
 void
 hugepage_allocator::insert_into_free_set(mm_block_t* block)
 {
-    m_free_large.emplace(block->size,block);
+    m_free_large.insert( {block->size,block});
 }
 
 mm_block_t*