Add libdca

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
update package libpng
update package vmime
package vmime: correct typo
package vmime: explicit options for iconv/icu choice

It should be easy for MXE users to choose between iconv and icu
by adjusting these options and the dependency list in vmime.mk.
update package vmime
update package lapack
update packge wavpack
update package gc
package wavpack: add missing exec_prefix in wavpack.pc

I get a build error in the xine-lib package after the latest wavpack
update because exec_prefix is not defined in wavpack.pc.
package boost: fix WinError capitalization
update package hdf5
update package wt
package openscenegraph: only update to stable releases
update package imagemagick
update package poco
package libnut: fix update placeholder
package sdl_ttf: ignore future 2x series updates
Merge pull request #273 from TimothyGu/dca

Add libdca
package libdca: fix update placeholder