OpenSystemsDevelopment / qpdf

Specify qpdf libraries before external ones.
Specify LDFLAGS before libraries.
This should eliminate remaining cases of qpdf builds favoring
previously installed versions.

Resolve link error on cygwin

Slightly improve memory cleanup in Pl_DCT
Make it easier to test with valgrind

Don't try to install HTML or PDF documentation if we're not building
docs.

Also separate C and C++ warning flags.

Some distributions (like debian) don't want .la files to be installed,
but the responsibility for doing this should like in the packaging,
not in qpdf itself.

Place user-specified CPPFLAGS and LDFLAGS later so that user-specified
non-standard paths that have old versions of qpdf don't cause the
build to fail.

For ELF systems, turn on versioned symbols by default, and add a
configure option to enable or disable them.

git-svn-id: svn+q:///qpdf/trunk@1058 71b93d88-0707-0410-a8cf-f5a4172ac649

git-svn-id: svn+q:///qpdf/trunk@854 71b93d88-0707-0410-a8cf-f5a4172ac649

git-svn-id: svn+q:///qpdf/trunk@776 71b93d88-0707-0410-a8cf-f5a4172ac649

git-svn-id: svn+q:///qpdf/trunk@763 71b93d88-0707-0410-a8cf-f5a4172ac649

git-svn-id: svn+q:///qpdf/trunk@760 71b93d88-0707-0410-a8cf-f5a4172ac649

git-svn-id: svn+q:///qpdf/trunk@759 71b93d88-0707-0410-a8cf-f5a4172ac649

git-svn-id: svn+q:///qpdf/trunk@753 71b93d88-0707-0410-a8cf-f5a4172ac649