clover: Fix build after llvm r325155 and r325160

clover: Fix build after llvm r325155 and r325160

r325155 ("Pass a reference to a module to the bitcode writer.")
and
r325160 ("Pass module reference to CloneModule")

change function interface from pointer to reference.

v2: Fix indentation (tab instead of spaces)

Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>
Reviewed-by: Francisco Jerez <currojerez@riseup.net>