ports/175813: [patch] mail/dovecot2 doesn't detect libstemmer or exttextcat

Patches to get dovecot2 with fts_lucene to work, because textproc/libexttextcat
has incremented its library name so configure, has trouble finding it.
libstemmer is incorporated into lib-clucene-contribs-lib.so in textproc/clucene

libextextcat has gone from:
    libexttextcat.so(.*) -> libexttextcat-1.0.so(.*)-> libexttextcat-2.0.so(.*)