Problem: building on OS X may failed

Solution: Add troubleshooting guidelines to resolve

(Relicensing statement added)

INSTALL

@@ -137,6 +137,17 @@ The simplest way to compile this package is:
   6. Often, you can also type `make uninstall' to remove the installed
      files again.
 
+OS X Builds - Documentation
+===========================
+
+Basic installation on OS X may fail in `Making all in doc' step. This
+error can be resolved by adding environment variable for shell.
+
+export XML_CATALOG_FILES=/usr/local/etc/xml/catalog 
+
+Write comamnd above in shell for instant resolve, or append command into
+shell profile file and reload for permanent resolve.
+
 Compilers and Options
 =====================
 

RELICENSE/jsyoo5b.md

+# Permission to Relicense under MPLv2 or any other OSI approved license chosen by the current ZeroMQ BDFL
+
+This is a statement by JaeSang Yoo
+that grants permission to relicense its copyrights in the libzmq C++
+library (ZeroMQ) under the Mozilla Public License v2 (MPLv2) or any other 
+Open Source Initiative approved license chosen by the current ZeroMQ 
+BDFL (Benevolent Dictator for Life).
+
+A portion of the commits made by the Github handle "JSYoo5B", with
+commit author "JaeSang Yoo <jsyoo5b@gmail.com>", are copyright of JaeSang Yoo.
+This document hereby grants the libzmq project team to relicense libzmq, 
+including all past, present and future contributions of the author listed above.
+
+JaeSang Yoo  
+2020.02.29