[AVRO-3945] Add missing override

[mkmkme]

This issue has been reported by cppcheck:

impl/FileStream.cc:52:5: style: Struct 'FileBufferCopyIn' has a constructor with 1 argument that is not explicit. [noExplicitConstructor]
    FileBufferCopyIn(const char *filename) : h_(::CreateFileA(filename, GENERIC_READ, 0, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL)) {
    ^
impl/FileStream.cc:235:5: style: Struct 'FileBufferCopyOut' has a constructor with 1 argument that is not explicit. [noExplicitConstructor]
    FileBufferCopyOut(const char *filename) : h_(::CreateFileA(filename, GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL)) {
    ^
impl/FileStream.cc:62:10: style: The function 'seek' overrides a function in a base class but is not marked with a 'override' specifier. [missingOverride]
    void seek(size_t len) {
         ^
impl/FileStream.cc:45:18: note: Virtual function in base class
    virtual void seek(size_t len) = 0;
                 ^
impl/FileStream.cc:62:10: note: Function in derived class
    void seek(size_t len) {
         ^
impl/FileStream.cc:68:10: style: The function 'read' overrides a function in a base class but is not marked with a 'override' specifier. [missingOverride]
    bool read(uint8_t *b, size_t toRead, size_t &actual) {
         ^
impl/FileStream.cc:46:18: note: Virtual function in base class
    virtual bool read(uint8_t *b, size_t toRead, size_t &actual) = 0;
                 ^
impl/FileStream.cc:68:10: note: Function in derived class
    bool read(uint8_t *b, size_t toRead, size_t &actual) {
         ^
impl/FileStream.cc:245:10: style: The function 'write' overrides a function in a base class but is not marked with a 'override' specifier. [missingOverride]
    void write(const uint8_t *b, size_t len) {
         ^
impl/FileStream.cc:229:18: note: Virtual function in base class
    virtual void write(const uint8_t *b, size_t len) = 0;
                 ^
impl/FileStream.cc:245:10: note: Function in derived class
    void write(const uint8_t *b, size_t len) {

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

Documentation

• Does this pull request introduce a new feature? no

[mkmkme]

Does the Avro workflow require one PR per one task? Or can a JIRA issue have multiple PRs? I'd rather create a PR for each stage described in the ticket.

[martin-g]

Does the Avro workflow require one PR per one task? Or can a JIRA issue have multiple PRs? I'd rather create a PR for each stage described in the ticket.

Several PRs for each task is fine!

[martin-g]

Thank you, @mkmkme !

I will not backport it to branch-1.11 - there are talks at dev@ about releasing 1.12.