Add missing code blocks for some standard library references

Author: Rageking8

docs/standard-library/basic-ostream-class.md

@@ -449,12 +449,14 @@ int main()
 
 The nested class describes an object whose declaration structures the formatted output functions and the unformatted output functions.
 
+```cpp
 class sentry {
    public:
    explicit sentry(basic_ostream\<Elem, Tr>& _Ostr);
    operator bool() const;
    ~sentry();
    };
+```
 
 ### Remarks
 

docs/standard-library/bernoulli-distribution-class.md

@@ -161,6 +161,7 @@ The second constructor constructs an object whose stored parameters are initiali
 
 Contains the parameters of the distribution.
 
+```cpp
 struct param_type {
    typedef bernoulli_distribution distribution_type;
    param_type(double p = 0.5);
@@ -169,6 +170,7 @@ struct param_type {
    bool operator==(const param_type& right) const;
    bool operator!=(const param_type& right) const;
    };
+```
 
 ### Parameters
 

docs/standard-library/condition-variable-enums.md

@@ -11,7 +11,9 @@ ms.assetid: f261ad79-e25b-4afa-9f8a-909ce697e0d8
 
 Supplies symbolic names for the return values of the methods of class template [condition_variable](../standard-library/condition-variable-class.md).
 
+```cpp
 class cv_status {
    no_timeout
    timeout
 };
+```

docs/standard-library/negative-binomial-distribution-class.md

@@ -224,6 +224,7 @@ The second constructor constructs an object whose stored parameters are initiali
 
 Stores the parameters of the distribution.
 
+```cpp
 struct param_type {
    typedef negative_binomial_distribution`<`result_type> distribution_type;
    param_type(result_type k = 1, double p = 0.5);
@@ -233,6 +234,7 @@ struct param_type {
    bool operator==(const param_type& right) const;
    bool operator!=(const param_type& right) const;
    };
+```
 
 ### Parameters