Update project file deployment target to iOS 7 for 64-bit builds.

Reviewed By: chrisp

Test Plan: Built via XCode 5.
Facebook iOS SDK 3.9

Summary:
     see https://developers.facebook.com/ios/change-log-3.x/

Upgrading from 3.8
     https://developers.facebook.com/docs/ios/upgrading-from-3.8-to-3.9/

Reviewed By: jacl

Test Plan: Release Testing.

@update-submodule: vendor/OCMock
Facebook iOS SDK 3.10

Summary:
     see https://developers.facebook.com/ios/change-log-3.x/

Upgrading from 3.9
     https://developers.facebook.com/docs/ios/upgrading-from-3.9-to-3.10/

Reviewed By: jacl

Test Plan: Release Testing.
Facebook iOS SDK 3.11

Summary:
     see https://developers.facebook.com/ios/change-log-3.x/

Upgrading:
     https://developers.facebook.com/docs/ios/upgrading/

Reviewed By: jacl

Test Plan: Release Testing.
Facebook iOS SDK 3.11.1

Summary:
    see https://developers.facebook.com/ios/change-log-3.x/

Upgrading:
    https://developers.facebook.com/docs/ios/upgrading/

Reviewed By: jacl

Test Plan: Release Testing.
Facebook iOS SDK 3.12

Summary:
    see https://developers.facebook.com/ios/change-log-3.x/

Upgrading:
    https://developers.facebook.com/docs/ios/upgrading/
Facebook iOS SDK 3.13

Summary:
    see https://developers.facebook.com/ios/change-log-3.x/

Upgrading:
    https://developers.facebook.com/docs/ios/upgrading/
Facebook iOS SDK 3.13.1

Summary:
    see https://developers.facebook.com/ios/change-log-3.x/

Upgrading:
    https://developers.facebook.com/docs/ios/upgrading/