use new global, "Version", rather than macro, VERSION

use new global, "Version", rather than macro, VERSION

With this change, a version-string update no longer
forces recompilation of 100+ src/*.o files.
* src/version.c (Version): New global.  New file.
* src/version.h: Declare it.
* src/Makefile.am: Put it in a library that everyone links to.
(noinst_LIBRARIES, libver_a_SOURCES): Define.
(LDADD): Add libver.a.
(sc_tight_scope): Use perl (was sed), and a more relaxed regexp
to build the global-variable-name-recognizing regexp list.
* src/system.h: Include "version.h".
(case_GETOPT_VERSION_CHAR): Use Version rather than VERSION.
* src/basename.c (main): Use Version rather than VERSION.
* src/chroot.c (main): Likewise.
* src/cksum.c (main): Likewise.
* src/dd.c (main): Likewise.
* src/dirname.c (main): Likewise.
* src/echo.c (main): Likewise.
* src/hostid.c (main): Likewise.
* src/hostname.c (main): Likewise.
* src/link.c (main): Likewise.
* src/logname.c (main): Likewise.
* src/nice.c (main): Likewise.
* src/nohup.c (main): Likewise.
* src/printenv.c (main): Likewise.
* src/printf.c (main): Likewise.
* src/pwd.c (main): Likewise.
* src/setuidgid.c (main): Likewise.
* src/sleep.c (main): Likewise.
* src/sync.c (main): Likewise.
* src/test.c (main): Likewise.
* src/timeout.c (main): Likewise.
* src/true.c (main): Likewise.
* src/tsort.c (main): Likewise.
* src/unlink.c (main): Likewise.
* src/uptime.c (main): Likewise.
* src/users.c (main): Likewise.
* src/whoami.c (main): Likewise.
* src/yes.c (main): Likewise.