base.bbclass: attempt to fix the staging .la problem

base.bbclass: attempt to fix the staging .la problem
  - when using oe_libinstall to install a libtool library (.la file
  - present) into the staging directory (${STAGING_LIBDIR}) fix up the
  - installed .lai file so that it contains 'installed=no' - this
  - prevents libtool from subsequently using a copy of the build system
  - library if it exists in the final (target) installation directory
  - on the build machine (typically /usr/lib).  Remove the patches from
  - pcre_4.4.bb to match (it now seems to work without them), add
  - cherokee to the openslug (etc) build (it was failing because of this
  - problem.)