Apply patches to build on DragonFly BSD and (older) FreeBSD

This now makes ksh build on DragonFly BSD.

bin/package, src/cmd/INIT/package.sh:
- DragonFly also needs the -lm hack for LDFLAGS.

src/cmd/ksh93/sh/main.c, src/cmd/ksh93/tests/basic.sh:
- fixargs() doesn't work on DragonFly either
  (re: 9b7c392a, 159fb9ee, cefe087d).

The following are backported from:
https://github.com/att/ast/issues/26#issuecomment-313927854
https://github.com/att/ast/pull/19

src/lib/libast/comp/setlocale.c:
- Add missing #include <errno.h> since errno is used.

src/lib/libast/features/standards:
- Do not set any standards macros (_POSIX_SOURCE etc) on FreeBSD or
  DragonflyBSD; they disable too much functionality on those.

src/lib/libast/features/wchar:
- Set _STDFILE_DECLARED on DragonFly, too.

src/lib/libast/include/sfio.h, src/lib/libast/include/sfio_t.h,
src/lib/libast/sfio/_sfopen.c, src/lib/libast/sfio/sfclrlock.c,
src/lib/libast/sfio/sfhdr.h, src/lib/libast/sfio/sfnew.c,
src/lib/libast/sfio/sfset.c:
- Rename SF_* macros to SFIO_* to avoid a conflict with system
  headers.

src/lib/libast/string/strexpr.c:
- Rename error() to err() to avoid a conflict.

src/lib/libast/include/sfio.h

@@ -150,7 +150,7 @@ struct _sffmt_s
 #define SF_IOINTR	0040000	/* return on interrupts			*/
 #define SF_WCWIDTH	0100000	/* wcwidth display stream		*/
 
-#define SF_FLAGS	0177177	/* PUBLIC FLAGS PASSABLE TO SFNEW()	*/
+#define SFIO_FLAGS	0177177	/* PUBLIC FLAGS PASSABLE TO SFNEW()	*/
 #ifdef _typ_struct_sf_hdtr
 #define _SF_HIDESFFLAGS 1
 #endif
@@ -458,7 +458,7 @@ __INLINE__ ssize_t sfmaxr(ssize_t n, int s)	{ return __sf_maxr(n,s); }
 #endif /* _SFSTR_H */
 
 #ifdef _SF_HIDESFFLAGS
-#undef SF_FLAGS
-#define SF_FLAGS	0177177	/* PUBLIC FLAGS PASSABLE TO SFNEW()	*/
+#undef SFIO_FLAGS
+#define SFIO_FLAGS	0177177	/* PUBLIC FLAGS PASSABLE TO SFNEW()	*/
 #endif
 #endif /* _SFIO_H */

src/lib/libast/include/sfio_t.h

@@ -75,7 +75,7 @@
 	  (unsigned char*)(data),			/* endr		*/ \
 	  (unsigned char*)(data),			/* endb		*/ \
 	  (Sfio_t*)0,					/* push		*/ \
-	  (unsigned short)((type)&SF_FLAGS),		/* flags	*/ \
+	  (unsigned short)((type)&SFIO_FLAGS),		/* flags	*/ \
 	  (short)(file),				/* file		*/ \
 	  (unsigned char*)(data),			/* data		*/ \
 	  (ssize_t)(size),				/* size		*/ \