pidgin/pidgin

Add documentation for all PURPLE_TYPE_ functions as well as PURPLE_TUNE_ constants

Add document for all PURPLE_TYPE_ defines as well as PURPLE_TUNE_ constants

Testing Done:
Compile and doc build.

Reviewed at https://reviews.imfreedom.org/r/92/
if ENABLE_DOC
subdir('reference')
endif
if ENABLE_GTK
pidgin_man = configure_file(
input : 'pidgin3.1.in',
output : 'pidgin3.1',
configuration : man_conf,
install : true,
install_dir : get_option('mandir') + '/man1')
endif
if enable_consoleui
finch_man = configure_file(
input : 'finch3.1.in',
output : 'finch3.1',
configuration : man_conf,
install : true,
install_dir : get_option('mandir') + '/man1')
endif