Bitcoin-Qt: remove unneeded "--param ssp-buffer-size=1" flag

- that flag is not needed when using "-fstack-protector-all", so remove it
  (see:
  http://stackoverflow.com/questions/1629685/when-and-how-to-use-gccs-stack-protection-feature)

bitcoin-qt.pro

@@ -33,8 +33,8 @@ contains(RELEASE, 1) {
 
 !win32 {
 # for extra security against potential buffer overflows: enable GCCs Stack Smashing Protection
-QMAKE_CXXFLAGS *= -fstack-protector-all --param ssp-buffer-size=1
+QMAKE_CXXFLAGS *= -fstack-protector-all
-QMAKE_LFLAGS *= -fstack-protector-all --param ssp-buffer-size=1
+QMAKE_LFLAGS *= -fstack-protector-all
 # We need to exclude this for Windows cross compile with MinGW 4.2.x, as it will result in a non-working executable!
 # This can be enabled for Windows, when we switch to MinGW >= 4.4.x.
 }