Autoconf: Remove AC_PROG_GCC_TRADITIONAL

The use of AC_PROG_GCC_TRADITIONAL emits a warning with Autoconf 2.72.
Just remove it as AC_PROG_CC was already called, and as this macro has
had no useful effect since GCC dropped support for traditional-mode
compilation in version 3.3 (released in 2003), and the systems that
needed it are also long obsolete.

Author: Julien-Elie

configure.ac

@@ -370,7 +370,6 @@ AS_IF([`AS_ECHO(["=head1 test"]) | pod2text --guesswork=none > /dev/null 2>&1`],
 AC_SUBST(POD2TEXT_OPTION)
 
 dnl Checks for programs.
-AC_PROG_GCC_TRADITIONAL
 AC_PROG_LEX([noyywrap])
 AC_PROG_LN_S
 AC_PROG_MAKE_SET