pidgin/pidgin

Use LT_LIB_M to determine if we need to link to the math library and link Pidgin to the X11 libraries

Gentoo ran into an issue with the gold linker without -lm. The original patch
and work came from Justin Lechner. https://bugs.gentoo.org/386079

Gentoo also ran into an issue with X11_LIBS not being added to pidgin. This
should already be implicit everywhere except for homebrew which patches X11
out of their build. Original patch/work came from and. https://bugs.gentoo.org/500762

Testing Done:
Installed and ran locally.

Reviewed at https://reviews.imfreedom.org/r/608/
Purple, Pidgin and Finch
========================
See AUTHORS and COPYRIGHT for the list of contributors.
libpurple is a library intended to be used by programmers seeking
to write an IM client that connects to many IM networks. It supports
XMPP among other protocols.
Pidgin is a graphical IM client written in C which uses the GTK+
toolkit.
Finch is a text-based IM client written in C which uses the ncurses
toolkit.
BUILD
=====
Read the 'INSTALL' file for more detailed directions.
These programs use the standard ./configure ; make. You need to use
gmake, BSD make probably won't work. Remember, run ./configure --help
to see what build options are available.
In order to compile Pidgin you need to have GTK+ 2.0 installed (as
well as the development files!). The configure script will fail if you
don't. If you don't have GTK+ 2.0 installed, you should install it
using your distribution's package management tools.
For sound support, you also need gstreamer 0.10 or higher. For
spellchecking support, you need libgtkspell (http://gtkspell.sf.net/).
Your distro of choice probably already includes these, just be sure to
install the development packages.
RUN
===
You should run 'make install' as root to make sure plugins and other files
get installed into locations they want to be in. Once you've done that,
you only need to run 'pidgin' or 'finch'.
To get started, simply add a new account.
If you come across a bug, please report it at: http://developer.pidgin.im
PLUGINS
=======
If you do not wish to enable the plugin support within Purple, run the
./configure script with the --disable-plugins option and recompile your
source code. This will prevent the ability to load plugins.
'make install' puts the plugins in $PREFIX/lib/purple (PREFIX being what
you specified when you ./configure'd - it defaults to /usr/local). Purple
looks for the plugins in that directory by default. Plugins can be installed
per-user in ~/.purple/plugins as well. Pidgin and Finch also look in
$PREFIX/lib/pidgin and $PREFIX/lib/finch for UI-specific, respectively.
To build a plugin from a .c file, put it in the plugins/ directory in
the source and run 'make filename.so', e.g. if you have the .c file
'kickass.c', put it in the plugins/ directory, and from that directory,
run 'make kickass.so'.