gril: make ril_msg parameters 'const'

This change cleans up a TODO in the test-gril*
unit tests.  Basically all the ril_message
paramters in the grilreply and grilunsol functions
have now been changed to be 'const'.
unit: cleanup gril 'const' related TODOs

This change cleans up a number of 'const' related
TODOs in test-grilreply.c and test-grilunsol.c.
unit: test-grilunsol.c style cleanup
Merge pull request #27 from tonyespy/fix-gril-const-todo

Fix gril const todo