Apply by doing:
       cd /usr/src
       patch -p0 < 008_fortran.patch

However, that will not get the file onto your system in a convenient
way, since lots of recompilation would be needed to put the file in
place.  Instead, to get it onto your system, do the following:

       cd /usr/include
       ftp ftp://ftp.openbsd.org/pub/OpenBSD/patches/2.6/common/g2c.h

Index: include/Makefile
===================================================================
RCS file: /cvs/src/include/Makefile,v
retrieving revision 1.75
diff -u -r1.75 Makefile
--- include/Makefile    1999/10/05 22:29:36     1.75
+++ include/Makefile    1999/11/10 12:04:38
@@ -51,7 +51,7 @@

# Places using Makefile.bsd-wrapper that needs a prerequisite target met
# before includes
-PWDIRS=        ../lib/libssl ../usr.sbin/httpd
+PWDIRS=        ../lib/libssl ../usr.sbin/httpd ../gnu/egcs/libf2c

NOOBJ= noobj

Index: distrib/sets/lists/comp/mi
===================================================================
RCS file: /cvs/src/distrib/sets/lists/comp/mi,v
retrieving revision 1.121
diff -u -r1.121 mi
--- distrib/sets/lists/comp/mi  1999/11/07 20:28:46     1.121
+++ distrib/sets/lists/comp/mi  1999/11/10 12:04:59
@@ -603,6 +603,7 @@
./usr/include/g++/valarray
./usr/include/g++/vector
./usr/include/g++/vector.h
+./usr/include/g2c.h
./usr/include/glob.h
./usr/include/gmp.h
./usr/include/grp.h
Index: gnu/egcs/libf2c/Makefile.bsd-wrapper
===================================================================
RCS file: /cvs/src/gnu/egcs/libf2c/Makefile.bsd-wrapper,v
retrieving revision 1.2
diff -u -r1.2 Makefile.bsd-wrapper
--- gnu/egcs/libf2c/Makefile.bsd-wrapper        1999/08/24 00:20:14     1.2
+++ gnu/egcs/libf2c/Makefile.bsd-wrapper        1999/11/10 12:04:59
@@ -110,11 +110,6 @@
SRCS+= ${F77_SRCS:S/^/libF77\//}
SRCS+= ${VERSION_SRCS}

-depend:
-       cd ${.CURDIR}/../gcc && \
-               make -f Makefile.bsd-wrapper config.status tree-check.h
-       mkdir -p libE77
-
${.OBJDIR}/VersionI.c: libI77/Version.c
       ln -sf $> $@

@@ -129,6 +124,9 @@
#      CPPFLAGS=-I${.CURDIR}/../gcc/obj \

config.status: Makefile.in configure
+       mkdir -p libE77
+       cd ${.CURDIR}/../gcc && \
+               make -f Makefile.bsd-wrapper config.status tree-check.h
       # fake g771 existence
       cd $(EGCS_OBJDIR)/gcc && touch f771
       PATH="/bin:/usr/bin:/sbin:/usr/sbin" \
@@ -138,8 +136,13 @@
               --prefix=/usr --with-local-prefix=/usr ${CF} \
               && touch config.status

+# Configuring is needed for g2c.h to be built
+prereq depend: config.status
+
includes:
       install -C -o ${BINOWN} -g ${BINGRP} -m ${NONBINMODE} \
               ${.CURDIR}/f2c.h ${DESTDIR}/usr/include
+       install -C -o ${BINOWN} -g ${BINGRP} -m ${NONBINMODE} \
+               g2c.h ${DESTDIR}/usr/include

.include <bsd.lib.mk>