Look for no-krb5 and add the definition of NO_KRB5 if it's there.

I've no idea were the KRB5 header files and libraries are placed on
Win32.  When there's better knowledge, we might be able to process the
other KRB5-related arguments as well...

util/mk1mf.pl

@@ -60,6 +60,7 @@ and [options] can be one of
 	no-ssl2 no-ssl3				- Skip this version of SSL
 	just-ssl				- remove all non-ssl keys/digest
 	no-asm 					- No x86 asm
+	no-krb5					- No KRB5
 	nasm 					- Use NASM for x86 asm
 	gaswin					- Use GNU as with Mingw32
 	no-socks				- No socket code
@@ -216,6 +217,7 @@ $cflags.=" -DNO_SOCK" if $no_sock;
 $cflags.=" -DNO_SSL2" if $no_ssl2;
 $cflags.=" -DNO_SSL3" if $no_ssl3;
 $cflags.=" -DNO_ERR"  if $no_err;
+$cflags.=" -DNO_KRB5"  if $no_krb5;
 #$cflags.=" -DRSAref"  if $rsaref ne "";
 
 ## if ($unix)
@@ -869,6 +871,7 @@ sub read_options
 	elsif (/^no-ssl3$/)	{ $no_ssl3=1; }
 	elsif (/^no-err$/)	{ $no_err=1; }
 	elsif (/^no-sock$/)	{ $no_sock=1; }
+	elsif (/^no-krb5$/)	{ $no_krb5=1; }
 
 	elsif (/^just-ssl$/)	{ $no_rc2=$no_idea=$no_des=$no_bf=$no_cast=1;
 				  $no_md2=$no_sha=$no_mdc2=$no_dsa=$no_dh=1;