This patch implements an authentication module based on the
PolarSSL library (v1.3.9) to verify the Chain of Trust when
Trusted Boot is enabled.

PolarSSL sources must be fetched separately. The POLARSSL_DIR
build option may be used to indicate the path to the PolarSSL
main directory (this directory must contain the 'include' and
'library' subdirectories).

To be able to build PolarSSL sources as a part of the Trusted
Firmware build process, the DISABLE_PEDANTIC flag in polarssl.mk
will tell the build system to remove the -pedantic option from
the CFLAGS.

Inclusion of PolarSSL increases the memory requirements of the BL1
and BL2 images. The following are the changes made to the FVP and
Juno platforms to cater for this when TRUSTED_BOARD_BOOT is
defined:

Changes on FVP:

  - BL1 and BL2 stacks have been increased to 4 KB
  - BL1(rw) section has been increased to 32 KB.
  - BL2 memory region has been increased to 112 KB

Changes on Juno:

  - BL1 and BL2 stack...