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/
SUBDIRS = api loader
mono_sources = GetBuddyBack.cs \
MPlugin.cs
EXTRA_DIST = $(mono_sources)
monodir = $(libdir)/purple-$(PURPLE_MAJOR_VERSION)
mono_SCRIPTS = MPlugin.dll GetBuddyBack.dll
mono_build_sources = $(addprefix $(srcdir)/, $(mono_sources))
all: $(mono_SCRIPTS)
SUFFIXES = .cs .dll
.cs.dll: api/PurpleAPI.dll $(mono_build_sources)
mcs -t:library -lib:./api -out:$@ -r:PurpleAPI.dll $<
clean-local:
rm -f $(mono_SCRIPTS)