There was a mess made when remote synthesis
data were specified as hdlmake's run arguments.
Makefile was incorrect and remote synthesis was
impossible.

Hdlmake will now produce makefiles that have
correct dependencies for .sv and .v files.
vcom_opt variable from manifests will be taken
into account when looking for files from
`include clauses

Proper ISE version is detetcted basing on XILINX variable.
Afterwards, a path to ISE installtion (default) is put
into the makefile.