Cleanup leftovers from migrating depends from bitcoin

Depends still contained some leftovers, like the `wallet` target that
included bdb from bitcoin. This commit removes these unneeded targets,
the miniupnpc package and the berkeley db package. Reflect the changes
in the README as well.

contrib/depends/Makefile

@@ -3,9 +3,6 @@
 SOURCES_PATH ?= $(BASEDIR)/sources
 BASE_CACHE ?= $(BASEDIR)/built
 SDK_PATH ?= $(BASEDIR)/SDKs
-NO_QT ?=
-NO_WALLET ?=
-NO_UPNP ?=
 FALLBACK_DOWNLOAD_PATH ?= https://bitcoincore.org/depends-sources
 
 BUILD = $(shell ./config.guess)
@@ -97,17 +94,10 @@ $(host_arch)_$(host_os)_id_string+=$(shell $(host_CXX) --version 2>/dev/null)
 $(host_arch)_$(host_os)_id_string+=$(shell $(host_RANLIB) --version 2>/dev/null)
 $(host_arch)_$(host_os)_id_string+=$(shell $(host_STRIP) --version 2>/dev/null)
 
-qt_packages_$(NO_QT) = $(qt_packages) $(qt_$(host_os)_packages) $(qt_$(host_arch)_$(host_os)_packages)
-wallet_packages_$(NO_WALLET) = $(wallet_packages)
-upnp_packages_$(NO_UPNP) = $(upnp_packages)
 
-packages += $($(host_arch)_$(host_os)_packages) $($(host_os)_packages) $(qt_packages_) $(wallet_packages_) $(upnp_packages_)
+packages += $($(host_arch)_$(host_os)_packages) $($(host_os)_packages)
 native_packages += $($(host_arch)_$(host_os)_native_packages) $($(host_os)_native_packages)
 
-ifneq ($(qt_packages_),)
-native_packages += $(qt_native_packages)
-endif
-
 all_packages = $(packages) $(native_packages)
 
 meta_depends = Makefile funcs.mk builders/default.mk hosts/default.mk hosts/$(host_os).mk builders/$(build_os).mk
@@ -153,9 +143,6 @@ $(host_prefix)/share/config.site : config.site.in $(host_prefix)/.stamp_$(final_
             -e 's|@CPPFLAGS@|$(strip $(host_CPPFLAGS) $(host_$(release_type)_CPPFLAGS))|' \
             -e 's|@LDFLAGS@|$(strip $(host_LDFLAGS) $(host_$(release_type)_LDFLAGS))|' \
             -e 's|@allow_host_packages@|$(ALLOW_HOST_PACKAGES)|' \
-            -e 's|@no_qt@|$(NO_QT)|' \
-            -e 's|@no_wallet@|$(NO_WALLET)|' \
-            -e 's|@no_upnp@|$(NO_UPNP)|' \
             -e 's|@debug@|$(DEBUG)|' \
             $< > $@
 	$(AT)touch $@
@@ -176,9 +163,6 @@ $(host_prefix)/share/toolchain.cmake : toolchain.cmake.in $(host_prefix)/.stamp_
             -e 's|@CPPFLAGS@|$(strip $(host_CPPFLAGS) $(host_$(release_type)_CPPFLAGS))|' \
             -e 's|@LDFLAGS@|$(strip $(host_LDFLAGS) $(host_$(release_type)_LDFLAGS))|' \
             -e 's|@allow_host_packages@|$(ALLOW_HOST_PACKAGES)|' \
-            -e 's|@no_qt@|$(NO_QT)|' \
-            -e 's|@no_wallet@|$(NO_WALLET)|' \
-            -e 's|@no_upnp@|$(NO_UPNP)|' \
             -e 's|@debug@|$(DEBUG)|' \
             -e 's|@depends@|$(host_cmake)|' \
             -e 's|@prefix@|$($(host_arch)_$(host_os)_prefix)|'\