enc2xs needs portable way to know it's in the core

[Craig A. Berry]

This is a not entirely portable revision of a completely unportable method 
of determining whether enc2xs is being run during a core build, but it does 
allow the build to proceed on VMS.  Can't the extensions that use enc2xs 
pass it a parameter of PERL_CORE=$(PERL_CORE) or similar?  

--- ext/Encode/bin/enc2xs;-0    Sun Mar 31 15:05:56 2002
+++ ext/Encode/bin/enc2xs       Mon Apr  1 14:20:56 2002
@@ -1,7 +1,7 @@
 #!./perl
 BEGIN {
-    # fiddle with @INC iff I am a part of perl dist
-    if ($^X =~ m/\bminiperl$/o){
+    # fiddle with @INC if I am a part of perl dist
+    if ($^X =~ m/miniperl(?:\.exe\;\d+)?$/o) {
        warn "Fixing \@INC for perl core.\n";
        unshift @INC, qw(../../lib ../../../lib ../../../../lib);
        $ENV{PATH} .= ';../..;../../..;../../../..' if $^O eq 'MSWin32';