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.

From now on, it shouldn't complain about a missing module,
if in fact it is already fetched

If a module has "fetchto" variable defined, then all
it's modules are fetched to this destination. If the
variable is indefined, then it is taken the parent.