add Intel C++ Compiler for Win32 support

-most fixes involve code detecting Perl on VC, and changing it to ICC
 is another kind of VC, but ICC's version isn't this "other kind of VC"'s
 version number, call the partner VC to find out the "VC version number"
 of ICC

not yet done
-no Intel C specific optimization flags
-long doubles and C99
-ccversion behavior might not be ideal/rethink