[Patch] MailProtocol.cpp: fix gcc6 build

[mt]

Gcc6 warns '-Werror=nonnull-compare' in some functions. It seems it is better to use BAutolock(this) than Blocker(this).

C++ /home/haiku/haiku/haiku/generated-gcc6/objects/haiku/x86/release/kits/mail/ssl/MailProtocol.o 
/home/haiku/haiku/haiku/src/kits/mail/MailProtocol.cpp: In member function 'bool BMailProtocol::AddFilter(BMailFilter*)':
/home/haiku/haiku/haiku/src/kits/mail/MailProtocol.cpp:91:21: error: nonnull argument 'this' compared to NULL [-Werror=nonnull-compare]
  BLocker locker(this);
                     ^
/home/haiku/haiku/haiku/src/kits/mail/MailProtocol.cpp: In member function 'int32 BMailProtocol::CountFilter() const':
/home/haiku/haiku/haiku/src/kits/mail/MailProtocol.cpp:99:21: error: nonnull argument 'this' compared to NULL [-Werror=nonnull-compare]
  BLocker locker(this);
                     ^
/home/haiku/haiku/haiku/src/kits/mail/MailProtocol.cpp: In member function 'BMailFilter* BMailProtocol::FilterAt(int32) const':
/home/haiku/haiku/haiku/src/kits/mail/MailProtocol.cpp:107:21: error: nonnull argument 'this' compared to NULL [-Werror=nonnull-compare]
  BLocker locker(this);
                     ^
/home/haiku/haiku/haiku/src/kits/mail/MailProtocol.cpp: In member function 'BMailFilter* BMailProtocol::RemoveFilter(int32)':
/home/haiku/haiku/haiku/src/kits/mail/MailProtocol.cpp:115:21: error: nonnull argument 'this' compared to NULL [-Werror=nonnull-compare]
  BLocker locker(this);
                     ^
/home/haiku/haiku/haiku/src/kits/mail/MailProtocol.cpp: In member function 'bool BMailProtocol::RemoveFilter(BMailFilter*)':
/home/haiku/haiku/haiku/src/kits/mail/MailProtocol.cpp:123:21: error: nonnull argument 'this' compared to NULL [-Werror=nonnull-compare]
  BLocker locker(this);
                     ^
cc1plus: all warnings being treated as errors

[korli]

Includes order should be alphabetical.

[mt]

Replying to korli:

Includes order should be alphabetical.

Hi korli, I sorted headers and add name to BAutolocks.

[korli]

Applied in hrev50281.