Add missing description for RPM package (based on debian pkg description).

Review a little bit that description (removing C++ because Faust is for several languages).
Factorize the description with debian package's.

CMakeLists.txt

@@ -849,7 +849,9 @@ ELSE(WIN32 AND NOT UNIX)
 		SET(CPACK_GENERATOR "DEB;RPM")
 		#SET(CPACK_DEBIAN_PACKAGE_DEPENDS "python, python-numpy, libfftw3-3, libsndfile1")
 		#SET(CPACK_DEBIAN_PACKAGE_SECTION "math")
-		SET(CPACK_DEBIAN_PACKAGE_DESCRIPTION "FAuST is a C++ toolbox, useful to decompose a given dense matrix into a product of sparse matrices in order to reduce its computational complexity (both for storage and manipulation). ")
+		SET(PACKAGE_DESCRIPTION "FAuST is a toolbox for decomposing a given dense matrix into a product of sparse matrices in order to reduce its computational complexity (both for storage and manipulation).")
+		SET(CPACK_DEBIAN_PACKAGE_DESCRIPTION "${PACKAGE_DESCRIPTION}")
+		SET(CPACK_RPM_PACKAGE_DESCRIPTION "${PACKAGE_DESCRIPTION}")
 		file(REMOVE ${PROJECT_BINARY_DIR}/postinst) # needed to remove possible postinstall script left here 
 							       # really needed only when BUILD_WRAPPER_MATLAB==OFF and BUILD_WRAPPER_PYTHON==ON
 	        if(BUILD_WRAPPER_MATLAB)
@@ -886,7 +888,7 @@ SET(CPACK_RPM_PACKAGE_LICENSE "GNU AFFERO GENERAL PUBLIC LICENSE")
 set(CPACK_RPM_PACKAGE_GROUP "unknown")
 set(CPACK_RPM_PACKAGE_VENDOR ${CPACK_PACKAGE_VENDOR})
 set(CPACK_RPM_PACKAGE_URL ${CPACK_PACKAGE_URL} )
-set(CPACK_RPM_PACKAGE_DESCRIPTION ${CPACK_PACKAGE_DESCRIPTION_SUMMARY})
+#set(CPACK_RPM_PACKAGE_DESCRIPTION ${CPACK_PACKAGE_DESCRIPTION_SUMMARY})
 		IF(CMAKE_SIZEOF_VOID_P MATCHES "4")
 			if(NOT DEFINED CPACK_PACKAGE_FILE_NAME)
 				SET(CPACK_PACKAGE_FILE_NAME "FAUST-binary-${CPACK_PACKAGE_VERSION}-i386-Linux")