pidgin/pidgin

Make our windows builds usable from meson.
release-2.x.y
2021-04-19, Gary Kramlich
2ff89178eb3d
Make our windows builds usable from meson.

This creates our pkg-config files on windows as well as fixes an include in
pidgin.h which can cause some issues.

This isn't usable as is, as you need a machine-file and a pkg-config wrapper
to make this all work, but that will be updated in the win32-dev.7z file thats
on data.imfreedom.org.

Testing Done:
Compiled guifications2 (which now uses meson) on windows and verified it works.

Reviewed at https://reviews.imfreedom.org/r/615/
/** @page cmd-signals Command Signals
@signals
@signal cmd-added
@signal cmd-removed
@endsignals
@see cmds.h
@signaldef cmd-added
@signalproto
void (*cmd_added)(const char *command, PurpleCmdPriority priority,
PurpleCmdFlag flag);
@endsignalproto
@signaldesc
Emitted when a new command is added.
@param command The new command.
@param priority The priority of the new command.
@param flag The command flags.
@endsignaldef
@signaldef cmd-removed
@signalproto
void (*cmd_removed)(const char *command);
@endsignalproto
@signaldesc
Emitted when a command is removed.
@param command The removed command.
@endsignaldef
*/