Add "stdcpp.h" to bench1.cpp and bench2.cpp (GH #520)

This is the first of possibly two or three for Borland compilers. We have to be careful because its very easy to break something due to math overloads with other compilers like SunCC or XL/C

bench1.cpp

@@ -17,6 +17,7 @@
 #include "drbg.h"
 #include "rdrand.h"
 #include "padlkrng.h"
+#include "stdcpp.h"
 
 #if CRYPTOPP_MSC_VERSION
 # pragma warning(disable: 4355)

bench2.cpp

@@ -30,6 +30,7 @@
 #include "pssr.h"
 #include "oids.h"
 #include "randpool.h"
+#include "stdcpp.h"
 
 #if CRYPTOPP_MSC_VERSION
 # pragma warning(disable: 4505 4355)

nbtheory.cpp

@@ -10,9 +10,7 @@
 #include "algparam.h"
 #include "smartptr.h"
 #include "misc.h"
-
-#include <vector>
-#include <cmath>
+#include "stdcpp.h"
 
 #ifdef _OPENMP
 # include <omp.h>

stdcpp.h

@@ -48,6 +48,7 @@ namespace std {
 #include <cstddef>
 #include <cstring>
 #include <climits>
+#include <cmath>
 
 // uintptr_t and ptrdiff_t
 #if (__cplusplus < 201103L) && (!defined(_MSC_VER) || (_MSC_VER >= 1700))