Update windows-build.txt

Added jansson library installation steps

windows-build.txt

@@ -122,6 +122,28 @@ Edit the file \MinGW\lib\pkgconfig\libcurl.pc and change "-lcurl" to
 "-lcurl -lcurldll".
 Ref. http://old.nabble.com/gcc-working-with-libcurl-td20506927.html
 
+**************************************************************************************
+* Install libjansson                                                                 *
+**************************************************************************************
+Go to this url ==> http://www.digip.org/jansson/releases/
+Download the latest tar with library sources.
+Copy the jansson-X.X folder into your \MinGW\msys\1.0\home\
+Run the MinGW MSYS shell
+(Start Icon/keyboard key ==> All Programs ==> MinGW ==> MinGW Shell).
+Enter jansson-X.X dir, and type
+      ./configure
+      make
+      make check
+      make install
+Copy src/.libs/*.dll into \MinGW\bin
+Copy src/.libs/*.a, src/.libs/*.la, src/.libs/*.lai into \MinGW\lib
+Copy src/jansson.def into \MinGW\lib
+Copy src/*.h into \MinGW\include\jansson
+Copy jansson.pc into \MinGW\lib\pkgconfig
+
+(Source: http://www.digip.org/jansson/doc/dev/gettingstarted.html)
+(Source: https://groups.google.com/forum/#!msg/jansson-users/CTPFBeZ0ZWQ/W3uuOuWZegkJ)
+
 **************************************************************************************
 * Build bfgminer.exe                                                                 *
 **************************************************************************************