eupspkg.sh: only look up variables with EUPSPKG_ prefix in the environ.

Currently, this applies to only three:

	EUPSPKG_REPOSITORY_PATH
	EUPSPKG_SOURCE
	EUPSPKG_VERBOSE

When specified on the command line, no EUPSPKG_ prefix should be used (i.e.,
eupspkg SOURCE=...  <verb>)
eupspkg.sh: support VERSION_PREFIX and VERSION_SUFFIX

$VERSION_PREFIX and $VERSION_SUFFIX are the prefix/suffix that
version_to_gitrev() removes from version before interpreting it as a git
rev (to be interpretable by git-rev-parse).

This lets one have a such as:

	hsc_1.2.3_c

that is converted into a 1.2.3 rev (which will, most likely, be a tag).

Also, when in DEVMODE autoversion() will prepend/append the _PREFIX, _SUFFIX
to the autogenerated version.

Environment variables EUPSPKG_VERSION_PREFIX and EUPSPKG_VERSION_SUFFIX will
be consulted if VERSION_{PREFIX|SUFFIX} are left unspecified.
eupspkg.sh: added copy_function() to enable calls to overridden functions
eupspkg.sh: prefer GITREV to SHA1, fix bugs with git-archive
eupspkg.sh: rename GITREV to REPOVERSION, fix tag->SHA1 resolution bug
eupspkg.sh: run fix_autoconf_timestamps only if not a TaP package
eupspkg.sh: non-intrusive site-specific customization of eupspkg scripts

The package distributor can have eupspkg.sh source a list of shell scripts
specified in a :-delimited string in SITECUSTOMIZE keyval argument (or
EUPSPKG_SITECUSTOMIZE environment variable).
eupspkg.sh: source EUPSPKG_SCRIPTS, and ./ups/eupspkg.cfg.sh by default

This removes the need for awkward boilerplate where ./ups/eupspkg would need
to source the eupspkg.sh library, then override variables/functions, and
then run the verbs.

Now it is the (former) library that is executed, which sources
./ups/eupspkg.cfg.sh and runs the requested verb.  The user can still
override this behavior by specifying their own ./ups/eupspkg.

Also renamed [EUPSPKG_]CONFIGS to [EUPSPKG_]SCRIPTS.
eupspkg.sh: TaP package improvements/bugfixes
eups_console: mechanism to echo messages to console

During 'eups distrib install', anything that's echoed to file descriptor 4
by ./ups/eupspkg script will be captured and echoed back to the user.

FDs 0 and 2 (stdin and stderr) are still captured in the log file and shown
only in case of error.
eupspkg.sh: call install_ups any time there's no $PREFIX/ups dir