gnu: libwpd: Fix build with newer GCC.

* gnu/packages/patches/libwpd-gcc-compat.patch: New file.
* gnu/local.mk (dist_patch_DATA): Adjust accordingly
* gnu/packages/libreoffice.scm (libwpd)[source](patches): New field.

gnu/local.mk

@@ -1422,6 +1422,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/libvpx-CVE-2016-2818.patch		\
   %D%/packages/patches/libxml2-xpath0-Add-option-xpath0.patch	\
   %D%/packages/patches/libxmlb-install-xb-tool-into-bindir.patch \
+  %D%/packages/patches/libwpd-gcc-compat.patch			\
   %D%/packages/patches/libxslt-generated-ids.patch		\
   %D%/packages/patches/libxt-guix-search-paths.patch		\
   %D%/packages/patches/lierolibre-check-unaligned-access.patch	\

gnu/packages/libreoffice.scm

@@ -236,6 +236,7 @@ (define-public libwpd
       (method url-fetch)
       (uri (string-append "mirror://sourceforge/libwpd/libwpd/"
                           "libwpd-" version "/libwpd-" version ".tar.xz"))
+      (patches (search-patches "libwpd-gcc-compat.patch"))
       (sha256 (base32
                "02fx8bngslcj7i5g1gx2kiign4vp09wrmp5wpvix9igxcavb0r94"))))
     (build-system gnu-build-system)

gnu/packages/patches/libwpd-gcc-compat.patch

@@ -0,0 +1,17 @@
+Fix build with newer GCC.
+
+Taken from upstream:
+
+  https://sourceforge.net/p/libwpd/code/ci/333c8a26f231bea26ec3d56245315041bbf5577f/
+
+--- a/src/lib/WPXTable.h
++++ b/src/lib/WPXTable.h
+@@ -53,7 +53,7 @@
+ 	~WPXTable();
+ 	void insertRow();
+ 	void insertCell(unsigned char colSpan, unsigned char rowSpan, unsigned char borderBits);
+-	const WPXTableCell  *getCell(size_t i, size_t j)
++	const WPXTableCell  *getCell(std::size_t i, std::size_t j)
+ 	{
+ 		return &(m_tableRows[i])[j];
+ 	}