build-sys: install all library manpages

A number of manpages were curiously omitted from the installation
process, but are referred to in installed manpages. To avoid developers
spontaneously combusting, ship all available manpages.
Model the pcre checks for the autotools build system to be similar as that used in the cmake build system.
Fix warning about unused variable triggered when not building on WIN32.
Fix warnings about redefinition of variables, use either sys/xattr.h or attr/xattr.h.
Cast comparison functions to __compar_fn_t if stdlib.h defines it.
Merge pull request #36 from falconindy/manpages

build-sys: install all library manpages
Initialize buff, fix valgrind warning about use of uninitialized bytes.
Change crypto checks, find necessary library before corresponding checks are done.
LIBS are set back to original value if all crypto checks for that implementation
fail.
Fix check for openssl on Windows.

OpenSSL libraries are named differently on Windows.
Remove the 4th argument to CRYPTO_CHECK, it is no longer used.
Update libarchive website location.
Bump version to 3.1.2.
Remove developer cflags.
Update NEWS file.
Reenable developer cflags.
Fix build failure of example program because of __FBSDID define.
Fixes #283
Signed-off-by: Andres Mejia <amejia004@gmail.com>
Set a default error message if message passed in is NULL.
Signed-off-by: Andres Mejia <amejia004@gmail.com>
Use correct define for libarchive version number in archive.h.
Signed-off-by: Andres Mejia <amejia004@gmail.com>
Set offset to correct data type.
Fixes #282
Signed-off-by: Andres Mejia <amejia004@gmail.com>
Add a convenience function to sort a list of strings.
This is useful for sorting a list of filepaths to
multivolume RARs for example.