TCL/TK configuration fixes for PostgreSQL 6.4

The TCL/TK configuration cleanup patches I submitted have the following
problem:

    'tclsh' still had to be found even if --with-libs (or --with-libraries) was
    specified to configure.

    --with-libs is really an overloaded option.  It really should only be used
    to specify additions directories to search in order to file needed
    libraries.  It was also being used to locate the *Config.sh files.

This patch addresses these problems by:

1.  Creating a new option (--with-tclconfig) which is used to specify the
    location of the *Config.sh files.  If the tkConfig.sh is located in a
    different location than the tclConfig.sh, you can give both locations
    seperated by a space.  For example:

        --with-tclconfig="/opt/lib/tcl8.0 /opt/lib/tk8.0"

2.  Changing the search logic so that if '--with-tclconfg' is specified, then
    the tcl shell program is not used to obtain a list of directories to search
    for the *Config.sh files.  It is assumed that the directories given with
    the --with-tclconfig option will contain the *Config.sh files.

3.  Adding 'tcl' as a name of the tcl shell program to be searched for if
    'tclsh' was not found in the PATH.  This seems to be another common name
    for the tcl shell program.

This patch also moves the clean-up of the generated Makefile.tcldefs and
Makefile.tkdefs in bin/pgtclsh from GNUmakefile.in to the Makefile in
bin/pgtclsh (where, IMHO, they belong).
____       | Billy G. Allie    | Domain....: Bill.Allie@mug.org
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