* macros/pcre.m4 (PCRE_CHECK_UTF8): Make sure the preprocessor
directives in the test program start in the first column, just
in case we do hit on some ancient compiler that requires it.

* macros/misc.m4 (REGEXXER_LIB_POPT): New macro that checks
whether libpopt and popt.h are available and usable.

* configure.ac: Use REGEXXER_LIB_POPT().
* src/Makefile.am (regexxer_LDADD): Add $(POPT_LIBS).

* src/mainwindow.{cc,h} (InitState): New struct that defines
the initial state of main window's entry boxes and check buttons.
(MainWindow::initialize): New method to initialize the UI elements
with the values defined by a InitState object.

* src/translation.{cc,h} (initialize_gettext): Remove the call to
bind_textdomain_codeset().
(enable_utf8_gettext): New function that calls
bind_textdomain_codeset() if available.  The separation became
necessary in order to allow for the command line help message to
be printed to the console in locale encoding.

* src/main.cc (parse_command_line): New function which parses the
command line arguments and returns an InitState object.
(main): Invoke parse_command_line(), enable_utf8_gettext() and
MainWindow::initialize() as appropriate.