man: Fix a typo of an argument.

ompi/mpi/man/man3/MPI_Compare_and_swap.3in

@@ -13,7 +13,7 @@
 .SH C Syntax
 .nf
 #include <mpi.h>
-int MPI_Compare_and_swap(const void *\fIorigin_addr\fP, const void *\fIcompar_addr\fP,
+int MPI_Compare_and_swap(const void *\fIorigin_addr\fP, const void *\fIcompare_addr\fP,
 	void *\fIresult_addr\fP, MPI_Datatype \fIdatatype\fP, int \fItarget_rank\fP,
 	MPI_Aint \fItarget_disp\fP, MPI_Win \fIwin\fP)