mandoc: fix segfaults with some pages (See #273)

extra/mandoc/build

@@ -1,6 +1,7 @@
 #!/bin/sh -e
 
 patch -p1 < mandoc-no-warn.patch
+patch -p1 < fix-tbl-segfault.patch
 
 # Change default pager.
 sed 's,"more -s","less",g' main.c > _

extra/mandoc/checksums

@@ -1,2 +1,3 @@
 8219b42cb56fc07b2aa660574e6211ac38eefdbf21f41b698d3348793ba5d8f7
 eaff34c03d1b6741cf6b24a394c63ad6096e4391578414b9da986294ee817a25
+12e6138be6ec2e8a34373876d8a5fce387a1d2b51a461ae20e1d98637af1d15c

extra/mandoc/patches/fix-tbl-segfault.patch

@@ -0,0 +1,20 @@
+--- tbl_term.c	2020-08-18 12:35:27.290953791 +0200
++++ tbl_term.c	2020-08-18 12:35:23.450952148 +0200
+@@ -626,7 +626,7 @@
+ 
+ 		lw = cpp == NULL || cpn == NULL ||
+ 		    (cpn->pos != TBL_CELL_DOWN &&
+-		     (dpn == NULL || strcmp(dpn->string, "\\^") != 0))
++		     (dpn == NULL || dpn->pos == TBL_DATA_NONE || strcmp(dpn->string, "\\^") != 0))
+ 		    ? hw : 0;
+ 		tbl_direct_border(tp, BHORIZ * lw,
+ 		    col->width + col->spacing / 2);
+@@ -670,7 +670,7 @@
+ 
+ 		rw = cpp == NULL || cpn == NULL ||
+ 		    (cpn->pos != TBL_CELL_DOWN &&
+-		     (dpn == NULL || strcmp(dpn->string, "\\^") != 0))
++		     (dpn == NULL || dpn->pos == TBL_DATA_NONE || strcmp(dpn->string, "\\^") != 0))
+ 		    ? hw : 0;
+ 
+ 		/* The line crossing at the end of this column. */

extra/mandoc/sources

@@ -1,2 +1,3 @@
 https://fossies.org/linux/misc/mandoc-1.14.5.tar.gz
 patches/mandoc-no-warn.patch
+patches/fix-tbl-segfault.patch