+It verifies that dependencies are available, determines flags needed
+to compile and link against various required libraries, and identifies
+whether various system functions can be used or if locally-provided
+replacements will be built instead.
+
+Finally, it allows you to control various aspects of the build and
+installation process.
+
+First, some common variables can specified via environment variables:
+
+ CC The C compiler to use
+ CFLAGS Flags to pass to the C compiler
+ CPPFLAGS Flags to pass to the C preprocessor
+ CXX The C++ compiler to use
+ CXXFLAGS Flags to pass to the C compiler
+ LDFLAGS Flags to pass when linking
+
+Each of these values can further be controlled by specifying them
+later on the "make" command line.
+
+Other environment variables can be used to control configure itself,
+(and for which there is no equivalent build-time control):
+
+ XAPIAN_CONFIG The program to use to determine flags for
+ compiling and linking against the Xapian
+ library. [$XAPIAN_CONFIG]
+ PYTHON Name of python command to use in
+ configure and the test suite.
+
+Additionally, various options can be specified on the configure
+command line.
+
+ --prefix=PREFIX Install files in PREFIX [$PREFIX]
+
+By default, "make install" will install the resulting program to
+$PREFIX/bin, documentation to $PREFIX/man, etc. You can
+specify an installation prefix other than $PREFIX using
+--prefix, for instance:
+
+ ./configure --prefix=\$HOME
+
+Fine tuning of some installation directories is available:
+
+ --libdir=DIR Install libraries to DIR [PREFIX/lib]
+ --includedir=DIR Install header files to DIR [PREFIX/include]
+ --mandir=DIR Install man pages to DIR [PREFIX/share/man]
+ --sysconfdir=DIR Read-only single-machine data [PREFIX/etc]
+ --emacslispdir=DIR Emacs code [PREFIX/share/emacs/site-lisp]
+ --emacsetcdir=DIR Emacs miscellaneous files [PREFIX/share/emacs/site-lisp]
+ --bashcompletiondir=DIR Bash completions files [PREFIX/share/bash-completion/completions]
+ --zshcompletiondir=DIR Zsh completions files [PREFIX/share/zsh/functions/Completion/Unix]
+
+Some features can be disabled (--with-feature=no is equivalent to
+--without-feature) :
+
+ --without-bash-completion Do not install bash completions files
+ --without-docs Do not install documentation
+ --without-api-docs Do not install API man page
+ --without-emacs Do not install lisp file
+ --without-desktop Do not install desktop file
+ --without-ruby Do not install ruby bindings
+ --without-zsh-completion Do not install zsh completions files
+ --without-retry-lock Do not use blocking xapian opens, even if available
+
+Additional options are accepted for compatibility with other
+configure-script calling conventions, but don't do anything yet:
+
+ --build=<cpu>-<vendor>-<os> Currently ignored
+ --host=<cpu>-<vendor>-<os> Currently ignored
+ --infodir=DIR Currently ignored
+ --datadir=DIR Currently ignored
+ --localstatedir=DIR Currently ignored
+ --libexecdir=DIR Currently ignored
+ --disable-maintainer-mode Currently ignored
+ --disable-dependency-tracking Currently ignored
+
+EOF
+}
+
+# Parse command-line options