Revision 1818871

Don't use a prefix of "yes" for lz4/utf8proc detection

The --with-{lz4,utf8proc} configure switches have 3 supported uses
(--with-<lib>, --with-<lib>=internal, --with-<lib>=PREFIX).  Using
"--with-<lib>" was setting the prefix to "yes", when it should have
been using the "std" detection.

* build/ac-macros/lz4.m4
  (SVN_LZ4): Correctly set lz4_prefix with "--with-lz4"

* build/ac-macros/utf8proc.m4
  (SVN_UTF8PROC): Correctly set utf8proc_prefix with "--with-utf8proc"