I've added options support for libxml2.  Please make sure to keep that whole WITHOUT_THREADS business.  It gets tricky trying to undefined WITH_THREADS in tinderbuild.  I usually leave it defined and this port is the only that, as advertised, breaks other ports when built with threads.

Fix: 

PORTNAME=      libxml2
 PORTVERSION=   2.6.30
-PORTREVISION?= 0
+PORTREVISION?= 1
 CATEGORIES?=   textproc gnome
 MASTER_SITES=  ftp://xmlsoft.org/libxml2/ \
                ftp://fr.rpmfind.net/pub/libxml/
@@ -36,12 +36,25 @@
 CONFIGURE_ENV= CPPFLAGS="-I${LOCALBASE}/include" \
                LDFLAGS="-L${LOCALBASE}/lib"

+OPTIONS=       THREADS "Threadsafe (WILL BREAK PORTS LIKE PHP!)" off \
+               SCHEMA "Add XML schema support" on \
+               XMLLINT_HIST "Add history support xmllint tool" off \
+               THREAD_ALLOC "Per-thread memory (DEVELOPERS ONLY!)" off \
+               MEM_DEBUG "Memory debugging (DEVELOPERS ONLY!)" off
+
 .if !defined(MASTERDIR)
 MAN1=          xml2-config.1 xmllint.1 xmlcatalog.1
 MAN3=          libxml.3
 .endif

-.if defined(WITH_THREADS)
+
+.include <bsd.port.pre.mk>
+
+
+# We go through this !defined() because some people
+# add WITH_THREADS to make.conf (or tinderbuild, where
+# this is the only port that breaks with it enabled...)
+.if defined(WITH_THREADS) && !defined(WITHOUT_THREADS)
 CONFIGURE_ARGS+=       --with-threads
 .else
 CONFIGURE_ARGS+=       --without-threads
@@ -74,6 +87,6 @@
                 s|/etc/sgml/catalog|${LOCALBASE}/share/sgml/catalog|g' ${WRKSRC}/${f}
 .endfor

-.include <bsd.port.mk>
+.include <bsd.port.post.mk>

 .endif--FUlkbncChQD06nVcyjmQgS6FJZI39VcgkeA6WTeHCsw3nr5S
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--- Makefile.old        Fri Oct  5 22:10:56 2007
+++ Makefile    Fri Oct  5 22:30:00 2007
@@ -13,7 +13,7 @@