Default the definition of portASSERT_IF_IN_ISR() to nothing if it is not defined.

Default the definition of portASSERT_IF_IN_ISR() to nothing if it is not defined.
Helper updates to allow a count of the number of mutexes held to be added.
Updates to the CCS Cortex-R4 implementation necessitated by a change in compiler semantics.
Update PIC32MX and MZ ports to assert if a non ISR safe function is called from an ISR.

git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@2263 1d2547de-c912-0410-9cb9-b8ca96c0e9e2