Default src_prepare

Starting from EAPI="2", the src_prepare function is the appropriate area to perform any kind of patching and source code manipulation, instead of src_unpack.

src_prepare() {
	true;
}

Sample src_prepare

src_prepare() {
    epatch "${FILESDIR}/${PV}/${P}-fix-bogosity.patch"
    use pam && epatch "${FILESDIR}/${PV}/${P}-pam.patch"

    sed -i -e 's/"ispell"/"aspell"/' src/defaults.h || die "Sed failed!"
}