include/libxml2/libxml/encoding.h wants iconv.h, so teach

FindLibXml2.cmake how to find the libiconv include directory.

Problem spotted by landry@ while porting geo/pgpointcloud

devel/cmake/Makefile

@@ -1,4 +1,4 @@
-# $OpenBSD: Makefile,v 1.156 2017/04/21 18:37:43 kurt Exp $
+# $OpenBSD: Makefile,v 1.157 2017/07/04 16:38:53 dcoppa Exp $
 
 DPB_PROPERTIES =parallel
 
@@ -7,7 +7,7 @@ COMMENT =	portable build system
 VER =		3.7.2
 DISTNAME =	cmake-${VER}
 CATEGORIES =	devel
-REVISION =	0
+REVISION =	1
 
 HOMEPAGE =	https://www.cmake.org/
 

devel/cmake/patches/patch-Modules_FindLibXml2_cmake

@@ -0,0 +1,27 @@
+$OpenBSD: patch-Modules_FindLibXml2_cmake,v 1.1 2017/07/04 16:38:53 dcoppa Exp $
+
+include/libxml2/libxml/encoding.h wants iconv.h
+
+Index: Modules/FindLibXml2.cmake
+--- Modules/FindLibXml2.cmake.orig
++++ Modules/FindLibXml2.cmake
+@@ -18,6 +18,8 @@
+ #   LIBXML2_XMLLINT_EXECUTABLE - The XML checking tool xmllint coming with LibXml2
+ #   LIBXML2_VERSION_STRING - the version of LibXml2 found (since CMake 2.8.8)
+ 
++include(FindIconv)
++
+ # use pkg-config to get the directories and then use these values
+ # in the find_path() and find_library() calls
+ find_package(PkgConfig QUIET)
+@@ -50,6 +52,10 @@ elseif(LIBXML2_INCLUDE_DIR AND EXISTS "${LIBXML2_INCLU
+     string(REGEX REPLACE "^#define[\t ]+LIBXML_DOTTED_VERSION[\t ]+\"([^\"]*)\".*" "\\1"
+            LIBXML2_VERSION_STRING "${libxml2_version_str}")
+     unset(libxml2_version_str)
++endif()
++
++if(ICONV_FOUND)
++    list(INSERT LIBXML2_INCLUDE_DIR 0 ${ICONV_INCLUDE_DIR})
+ endif()
+ 
+ # handle the QUIETLY and REQUIRED arguments and set LIBXML2_FOUND to TRUE if