Fix porting guide references to platform.h

Following recent refactoring changes to platform.h, this commit updates
porting-guide.md to correctly refer to platform.h and platform_def.h where
appropriate.

Change-Id: Idf1e77503c24358696f8f3c14caa0cc1d579deb4
Documentation for BL3-1 hardening and reset vector

Update documentation with BL3-1 hardening interface
changes and for using BL3-1 as a reset vector feature

Change-Id: Iafdd05e7a8e66503409f2acc934372efef5bc51b
User guide updates for v0.4 release

Update the Linux kernel, Linaro file system, FVP and DS-5 versions used for the
v0.4 release in user-guide.md.

Change-Id: I2265fc17c229d4b8cc52165d6583a4a579cdcee3
Merge pull request #116 from 'danh-arm:dh/refactoring-docs'
Merge pull request #117 from 'danh-arm:dh/v0.4-user-guide'
Merge pull request #118 from 'vikramkanigiri:vk/doc_for_133'