The RMAPI_FUNC_SUPPORTED was defined in the wrong place on redismodule.h
and was not visible to modules.
(cherry picked from commit 560d2dc0081bc35b81b6a64d25c4077fa2e69ad9)
Adding a test for coverage for RM_Call in a new "misc" unit
to be used for various short simple tests
also solves compilation warnings in redismodule.h and fork.c
* create module API for forking child processes.
* refactor duplicate code around creating and tracking forks by AOF and RDB.
* child processes listen to SIGUSR1 and dies exitFromChild in order to
eliminate a valgrind warning of unhandled signal.
* note that BGSAVE error reply has changed.
valgrind error is:
Process terminating with default action of signal 10 (SIGUSR1)
