Tweak pkg-config setup to work with Autotools-based project

[ilumsden]

Resolves #50

This PR tweaks the pkg-config stuff for PerfFlow Aspect to allow an Autotools-based project (i.e., DYAD) to correctly load the C/C++ interface for PerfFlow. In particular, this PR does the following:

• Adds a static version of libperfflow_parser.so to the build. Note that this static library is not installed
• Tweaks the build of WeavePass to use this static library (resolves linking/lookup issues when using the Clang plugin)
• Removes WeavePass from the Libs entry of perfflowaspect.pc
• Adds -lssl and -lcrypto to the Libs entry of perfflowaspect.pc to prevent undefined symbol errors on SHA1
• Removes the content of the Cflags entry of perfflowaspect.pc
• Adds a new weavepass entry to perfflowaspect.pc. This entry's value is the path to libWeavePass.so

Additionally, in DYAD, I created the following m4 macro to actually load all the info from pkg-config into the Autotools-based build system:

AC_DEFUN([AX_PERFFLOW_ASPECT], [
    PKG_CHECK_MODULES([$1], [perfflowaspect],
        [
            $1_WEAVEPASS=`pkg-config --variable=weavepass perfflowaspect`
            if test ! -e "${$1_WEAVEPASS}"; then
                AC_MSG_ERROR([Cannot find libWeavePass.so!])
            fi
            $1_PLUGIN_CPPFLAGS="-Xclang -load -Xclang ${$1_WEAVEPASS} -fPIC"
            AC_MSG_NOTICE([Flags are ${$1_PLUGIN_CPPFLAGS}])
            AC_SUBST($1_WEAVEPASS)
            AC_SUBST($1_PLUGIN_CPPFLAGS)
            $2
        ],
        [
            $3
        ]
    )
])

In DYAD, this is put into config/ax_perfflow_aspect.m4. This file is not included in this PR, but I can include it if desired.