Remove ZIP_ER_ENCMISMATCH. Not necessary any longer.

Was never included in any release.

lib/zip.h

diff --git a/lib/zip.h b/lib/zip.h
index cf3edb2..2d283fe 100644
--- a/lib/zip.h
+++ b/lib/zip.h
@@ -129,7 +129,6 @@
 #define ZIP_ER_RDONLY        25  /* N Read-only archive */ 
 #define ZIP_ER_NOPASSWD      26  /* N No password provided */
 #define ZIP_ER_WRONGPASSWD   27  /* N Wrong password provided */
-#define ZIP_ER_ENCMISMATCH   28  /* N Encoding of name and comment do not match */
 
 /* type of system error value */