pidgin/pidgin

Use LT_LIB_M to determine if we need to link to the math library and link Pidgin to the X11 libraries
release-2.x.y
2021-04-11, Gary Kramlich
132d17234930
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/
prefix=@prefix@
exec_prefix=@exec_prefix@
libdir=@libdir@
includedir=@includedir@
datarootdir=@datarootdir@
datadir=@datadir@
sysconfdir=@sysconfdir@
Name: Pidgin (Gaim compatibility)
Description: Pidgin is a GTK2-based instant messenger application.
Version: @VERSION@
Requires: glib-2.0
Cflags: -I${pc_top_builddir}/${pcfiledir}/libpurple -I${pc_top_builddir}/${pcfiledir}/pidgin
Libs: ${pc_top_builddir}/${pcfiledir}/libpurple/libpurple.la