Rationalise ./configure
- borrow a lot of ideas from Michael ABBOTT ( http://sourceware.org/ml/crossgcc/2008-12/msg00030.html )
- should be conforming to POSIX 1003.1-2008, non compliance due to bashsims is to be considered a bug
- as a result, it now works with dash
- make a little easier to read in some places
- enforce 4-space indentation
- get rid of futile 'return $?'
- quote all variables assignments
- save and restore IFS prior to and after using alternate values
- simplify the TOOLS_TO_CHECK listing

What's left:
- provide a mean to actually _compare_ version numbers
- change the TOOLS_TO_CHECK pattern style to be able to use '|' in regexp

/trunk/configure | 243 127 116 0 ++++++++++++++++++++++++++++++++------------------------------
1 file changed, 127 insertions(+), 116 deletions(-)

 Correctly check for g++ existence.

 Copyright 2007 Yann E. MORIN <yann.morin.1998@anciens.enib.fr>

 Licensed to you as dmalloc-5.5.2 is.

 diff -dur dmalloc-5.5.2.orig/configure dmalloc-5.5.2/configure

 --- dmalloc-5.5.2.orig/configure	2007-05-18 11:40:31.000000000 +0200

 +++ dmalloc-5.5.2/configure	2007-05-18 11:42:02.000000000 +0200

 @@ -2643,7 +2643,7 @@

  # see if we actually have a CXX program

 -if test "$ac_cv_prog_CXX" = "" -o ! -x "$ac_cv_prog_CXX"; then

 +if test "$ac_cv_prog_CXX" = "" -o ! -x `which "$ac_cv_prog_CXX"`; then

      { echo "$as_me:$LINENO: WARNING: could not find C++ compiler $ac_cv_prog_CXX" >&5

  echo "$as_me: WARNING: could not find C++ compiler $ac_cv_prog_CXX" >&2;}

      enable_cxx=no