A couple of issues with the cl-ppcre version

I ran into a couple of issues building the maxima using the cl-ppcre branch.

First, in doc/info/common-lang-utf8.mk there is the line

    sed -i -e "s|^@documentencoding $(fcharset)|@documentencoding
$(tcharset)|ig" *.texi

The ig is a GNU extension that doesn't work on OSX.  I think just making
it g instead of ig should work everywhere.

Second, common-lang-utf8.mk by default wants to use recode because
urecode=true.  I don't have recode, so the build fails.  I do have
iconv, so setting urecode=false makes things work.

I suspect common-lang-utf8.mk needs to be built by configure so urecode
has the correct value.

Ray