tls_openssl: removed unused openssl/rand.h
tls_schannel: [style] use LF for EOL, not CR+LF
tls_schannel: [style] removed trailing spaces
autotools: export only public API for dynamic library
sha1: removed xmpp_ prefix from SHA1 symbols

Prefix was introduced in a981c0a as a workaround. Now, non-public API is
not exported, so this patch hides SHA1 symbols for dynamic library.
fix MSVC build
conn: [style] fixed spacing
autotools: fixed libstrophe's version

Repository contains tag 0.8.6, but version in configure.ac is still
0.8.5. So change it to the future release.
auth: fixed memory leaks in _handle_scram_sha1_challenge()
ctx: fixed memory leak in xmpp_log()

Also fixed 2 bugs:
  - only 1022 bytes of the message is printed when length is 1023.
  - va_end() must be called after va_copy() otherwise we get
    undefined behaviour according to C99.
autotools: added AC_CONFIG_MACRO_DIR
autotools: check for ssl.h if pkg-config failed

Some distros provides libssl without openssl.pc.
Refactored configure.ac, added pkg-config support
Added --with-pkgconfigdir
autotools: removed duplication in configure.ac
ChangeLog: set future version to 0.8.7