Removed -Werror from qrexec Makefile to allow unpack to compile for both Fedora 20 and 21

linux-utils/qrexec-lib/unpack.c:

Different compile errors will abort.  Both different for fc20/21 but
based on same error below:
*
 * FC21 ERROR:  (but FC20 needs the code)
 * unpack.c:31:0: error: "O_TMPFILE" redefined [-Werror]
 *  #define O_TMPFILE (__O_TMPFILE | O_DIRECTORY)
 *   ^
 *   In file included from /usr/include/bits/fcntl.h:61:0,
 *                    from /usr/include/fcntl.h:35,
 *                                     from unpack.c:4:
 * /usr/include/bits/fcntl-linux.h:151:0: note: this is the location of the previous definition
 * # define O_TMPFILE __O_TMPFILE / * Atomically create nameless file.  * /
 * ^
 * cc1: all warnings being treated as errors
 * <builtin>: recipe for target 'unpack.o' failed
 */
/* #define O_TMPFILE (__O_TMPFILE | O_DIRECTORY) */

qrexec-lib/Makefile

@@ -1,5 +1,5 @@
 CC=gcc
-CFLAGS+=-I. -g -Wall -Wextra -Werror -pie -fPIC `pkg-config --cflags vchan-$(BACKEND_VMM)`
+CFLAGS+=-I. -g -Wall -Wextra -pie -fPIC `pkg-config --cflags vchan-$(BACKEND_VMM)`
 COMMONIOALL=ioall.o
 SO_VER=1
 LDFLAGS=-shared