==how to port to a new platform==
0) generate voc.par file for the target platform(if it's not exist in src/par).
   you can do it by compiling vocparam, and running it as "./vocparam > voc.par"
1) generate voc, ocat, showdef source for target platform by running
   make -f makefile.gcc.<arch> port0
   (or copy corresponding voc.par to the source directory yourself, remove stage2 from port0 section of the makefile, and run make port0)
2) transfer source to a target platform and write
   make port1
   (or use a crosscompiler)
   now you have voc, showdef, and ocat binaries for your target platform
3) cp voc vocstatic
   make -f makefile for your target.
that's how I've done x86 port.
voc was originally run on x86_64.

notes** in practice everything is not always simple, because you may need to edit Unix.Mod, Args.Mod and SYSTEM.h, and put them to src/lib/system/gcc/<yourtarget>, and create new makefile for your target.


==how to add a new option==

define it in OPM as a constant before defopt is defined.
define a BOOLEAN variable in OPM which will describe if setting is set.
add handling of a new option in OPM.ScanOptions
set your BOOLEAN value in OPM.OpenPari (or in ScanOptions, after the CASE) so you can check it later.
check your boolean when necessary, (see useParFile in OPM.GetOptions)
add it in OPC.GenHeaderMsg function.

==known bugs==

when using SYSTEM.LSH(s, n) where s is SET, 
c compiler generates an error like
"error: duplicate 'unsigned'", 
that's because SET is defined as unsigned in SYSTEM.h,
while LSH is defined in SYSTEM.h as ((t)((unsigned t)(x)<<(n))), 
and it makes not possible to make SYSTEM.LSH with type SET.
I don't want to prohibit it at the parser level 
because C backend is only one of possible backends.
The solution currently is to cast set type to longint before lsh-ing it.
And then casting it back to set if necessary.
