Log Message:
Update libtool packages to 2.4.6.

Changes since 2.4.2 are too numerous to mention, with over 4,700 lines
in the ChangeLog file.  However, this release does at least fix a large
number of build failures on SmartOS, and doesn't appear to cause any
obvious regressions in bulk builds performed by Joerg and myself.

Some pkgsrc cleanups while here, including merging the MirBSD patches
correctly.  It couldn't be made much clearer how to properly integrate
patches here to ensure they are not lost.  Next time you might not be so
fortunate!