Add configCLEAR_TICK_INTERRUPT() to the IAR and RVDS Cortex-A9 ports.

Add configCLEAR_TICK_INTERRUPT() to the IAR and RVDS Cortex-A9 ports.
Replace LDMFD with POP instructions in IAR and RVDS Cortex-A9 ports.
Replace branch to address with indirect branch and exchange to address in register in the IAR and RVDS Cortex-A9 ports.

git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@2193 1d2547de-c912-0410-9cb9-b8ca96c0e9e2