Fix TCPConnection.m for iOS 7 by not redefining system constant errSSLClosedAbort

TCPConnection.m declares errSSLClosedAbort which is actually from the system headers but wasn't in old iOS SDKs. It looks like this has been available since at least iOS 5, but weirdly wasn't included by bringing in Security.h. As of iOS 7, that's brought in by default so this causes a build error on the new SDK.

This change modifies the define to check that we're on at least iOS5 and if so bring in SecureTransport.h instead of defining the constant ourselves.

This also brings makes MYNetwork refer to the latest version of the MYUtilities submodule - also necessary for building on iOS 7.