lang/gforth: unbreak the build in the -Werror=int-conversion mode

Missing ecvt() function prototype was causing couple of warnings
which had become hard errors with recent versions of GCC (14+).
Getting rid of USE_GCC, while desirable, is not straightforward
and requires more work.  While here, set the TEST_TARGET which is
part of the upstream's default ALL_TARGET, but we override that.

PR:	281238

lang/gforth/Makefile

@@ -20,10 +20,10 @@ USES=		gmake libtool:build localbase makeinfo
 USE_GCC=	yes
 USE_LDCONFIG=	${PREFIX}/lib/gforth/${PORTVERSION}/libcc-named
 GNU_CONFIGURE=	yes
-GNU_CONFIGURE_MANPREFIX=	${PREFIX}/share
 CONFIGURE_ENV=	GFORTHHIST=${WRKSRC}
 MAKE_ENV=	GFORTHHIST=${WRKSRC}
 ALL_TARGET=	kernel/version.fs more info
+TEST_TARGET=	check
 MAKE_JOBS_UNSAFE=yes
 
 STRIP=		#none

lang/gforth/files/patch-engine_forth.h

@@ -0,0 +1,11 @@
+--- engine/forth.h.orig	2013-10-11 21:31:28 UTC
++++ engine/forth.h
+@@ -490,7 +490,7 @@ extern double asinh(double r1);
+ extern double acosh(double r1);
+ #endif
+ #ifndef HAVE_ECVT
+-/* extern char* ecvt(double x, int len, int* exp, int* sign);*/
++extern char* ecvt(double x, int len, int* exp, int* sign);
+ #endif
+ #ifndef HAVE_MEMMOVE
+ /* extern char *memmove(char *dest, const char *src, long n); */