adding shared memory support.
adding shared memory support.

Following changes has been made to support shared memory:
1. added a new command line option : -a if set with any value it will enable shared memory mode. ex: afl-fuzz.exe -a yes
2. used createfilemapping calls for shared memory.
3. modified options if shared memory then output file will be shmem.
4. will be unmapped at exit.
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