Move build feature rules to separate file
Fix usage of obsolete HAIKU_BUILD_FEATURE_OPENSSL_ENABLED
MultiArch* rule: support optional architecture parameter
ArchitectureSetup: fix library map for secondary arch

The libraries where resolved to the library targets for the primary
architecture.
MergedDirectory: missing include
lib{network,package,shared,agg,icon}: secondary arch support
build features/bootstrap repo: support secondary arch

* Add rule FSplitPackageName. It splits a package name into port name
  and package suffix.
* FSetConditionsHold: Rename to FConditionsHold and replace the set
  parameter by a predicate rule parameter, thus adding more flexibility.
* FIsBuildFeatureEnabled: Use the faster check.
* Add rule FQualifiedBuildFeatureName. Given a build feature name, it
  prepends the current packaging architecture to yield a qualified
  feature name. Is used by the other build feature rules so that the
  same build feature can be configured differently for each arch.
* ExtractBuildFeatureArchives: The supplied list is now filtered via
  FFilterByBuildFeatures, allowing for build feature conditions in the
  list.
* Add rule InitArchitectureBuildFeatures. It is called early for each
  configured architecture, setting up some basic build features for it.
  "primary" is set for the primary architecture and a "secondary_<arch>"
  is set for each secondary architecture.
* BuildFeatures: Add secondary architecture support: Use the correct
  paths for libraries and headers (subdir for secondary architecture)
  and configure the icu and zlib sources only for the primary
  architecture.
* BootstrapPackageRepository: The package lists are now filtered via
  FFilterByBuildFeatures, allowing for build feature conditions in the
  lists.
* IsPackageAvailable, FetchPackage: Add secondary architecture support.
* HaikuPortsCross/x86_gcc2: Add icu and zlib x86 secondary packages.

The second stage Haiku cross devel package for the secondary
architecture can now be built.