Move the conditionally compiled gnucash setenv/unsetenv functions to

[David Hampton]

Log Message:
-----------
Move the conditionally compiled gnucash setenv/unsetenv functions
to lib/libc a where they belong.

Tags:
----
gnucash-gnome2-dev

Modified Files:
--------------
    gnucash:
        ChangeLog
        configure.in
    gnucash/lib/libc:
        Makefile.am
    gnucash/src/backend/file:
        sixtp-utils.c
    gnucash/src/backend/file/test:
        Makefile.am
        test-save-in-lang.c
    gnucash/src/core-utils:
        Makefile.am
        gw-core-utils-spec.scm
    gnucash/src/gnc-module:
        Makefile.am
        gnc-module.c

Added Files:
-----------
    gnucash/lib/libc:
        setenv.c
        setenv.h

Removed Files:
-------------
    gnucash/src/core-utils:
        core-utils.c
        core-utils.h