vlog95: Emit if using signed and add the number of errors to the output

In the starting comment say if the conversion was done with signed support.
If there were errors then add a comment at the end of the file that says
how many errors occurred and add a line after this that prevents the file
from running with out an error. This requires the user to see that errors
occurred and remove the offending line if they want to use the file anyway.
vlog95: Emit initial blocks for tasks or functions.

In SystemVerilog a task or function can initialize a variable in a task or
function. In Icarus this is done by creating an initial block that does
the assignment. We can translate this by emitting the initial block in the
enclosing module scope. This is not 100% correct since SystemVerilog
requires the initialization to be done before the other initial/always
blocks are processed. For SystemVerilog the current Icarus behavior is
incorrect, but even if it had a new process type that ran before the other
ones the best I can do for vlog95 is emit it before the normal module
processes which currently works.