Added std:: qualifiers to avoid compiler errors in some situations

dlib/bigint/bigint_kernel_2.cpp

@@ -1532,7 +1532,7 @@ namespace dlib
             const uint32 len = lhs->digits_used + rhs->digits_used;
             for (unsigned long i = 0; i < len; ++i)
             {
-                uint64 num1 = static_cast<uint64>(floor(a[i*2].real()+0.5));
+                uint64 num1 = static_cast<uint64>(std::floor(a[i*2].real()+0.5));
                 num1 += carry;
                 carry = 0;
                 if (num1 > 255)
@@ -1541,7 +1541,7 @@ namespace dlib
                     num1 = (num1&0xFF);
                 }
 
-                uint64 num2 = static_cast<uint64>(floor(a[i*2+1].real()+0.5));
+                uint64 num2 = static_cast<uint64>(std::floor(a[i*2+1].real()+0.5));
                 num2 += carry;
                 carry = 0;
                 if (num2 > 255)
@@ -1852,7 +1852,7 @@ namespace dlib
 
         // compute the complex root of unity w
         const t temp = pi2/len;
-        ct w = ct(cos(temp),sin(temp));
+        ct w = ct(std::cos(temp),std::sin(temp));
 
         ct w_pow = 1;
 
@@ -1905,7 +1905,7 @@ namespace dlib
 
         // compute the complex root of unity w
         const t temp = pi2/len;
-        ct w = ct(cos(temp),sin(temp));
+        ct w = ct(std::cos(temp),std::sin(temp));
 
         ct w_pow = 1;