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/cmd/ksh93/tests/basic.sh

@@ -711,7 +711,7 @@ getPsOutput() {
 	while [[ $actual == [[:space:]]* ]]; do actual=${actual#?}; done
 	while [[ $actual == *[[:space:]] ]]; do actual=${actual%?}; done
 }
-if	[[ ! $(uname -s) =~ ^(FreeBSD|SunOS)$ ]] &&
+if	[[ ! $(uname -s) =~ ^(FreeBSD|DragonFly|SunOS)$ ]] &&
 	getPsOutput "$$" &&
 	[[ "$SHELL $0" == "$actual"* ]]  # "$SHELL $0" is how shtests invokes this script
 then	expect='./atest 1 2'