pidgin/pidgin

Use G_DECLARE_DERIVABLE_TYPE for PurpleConversation and additional cleanups

The setters for PurpleConversation are kind of crappy because of the
conversation cache in the purple_conversations api, which we'll address at a
later time.

Testing Done:
Compiled and ran locally, parted a chat and just signed out to verify no new issues.

Reviewed at https://reviews.imfreedom.org/r/613/
#include <winver.h>
VS_VERSION_INFO VERSIONINFO
FILEVERSION @PURPLE_MAJOR_VERSION@,@PURPLE_MINOR_VERSION@,@PURPLE_MICRO_VERSION@,0
PRODUCTVERSION @PURPLE_MAJOR_VERSION@,@PURPLE_MINOR_VERSION@,@PURPLE_MICRO_VERSION@,0
FILEFLAGSMASK 0
FILEFLAGS 0
FILEOS VOS__WINDOWS32
FILETYPE VFT_APP
FILESUBTYPE VFT2_UNKNOWN
BEGIN
BLOCK "StringFileInfo"
BEGIN
BLOCK "040904B0"
BEGIN
VALUE "CompanyName", "The Pidgin developer community"
VALUE "FileDescription", "Finch UI library"
VALUE "FileVersion", "@PURPLE_VERSION@"
VALUE "InternalName", "libfinch"
VALUE "LegalCopyright", "Copyright (C) 1998-2014 The Pidgin developer community (See the COPYRIGHT file in the source distribution)."
VALUE "OriginalFilename", "libfinch-@PURPLE_API_VERSION@.dll"
VALUE "ProductName", "Finch"
VALUE "ProductVersion", "@PURPLE_VERSION@"
END
END
BLOCK "VarFileInfo"
BEGIN
VALUE "Translation", 0x409, 1200
END
END