Modify install prefix

src/QZXing.pri

@@ -258,15 +258,30 @@ symbian {
         Location
 }
 
-unix:!symbian {
-    maemo5 {
-        target.path = /opt/usr/lib
-    } else {
-        target.path = /usr/lib
+!symbian {
+    isEmpty(PREFIX) {
+        maemo5 {
+            target.path = /opt/usr/lib
+        } else {
+            target.path = /usr/lib
+        }
     }
 
     DEFINES += NOFMAXL
-    INSTALLS += target
+
+	# Installation
+	headers.files = qzxing.h QZXing_global.h
+	headers.path = $$PREFIX/include
+	target.path = $$PREFIX/lib
+	INSTALLS += headers target
+
+	# pkg-config support
+	CONFIG += create_pc create_prl no_install_prl
+	QMAKE_PKGCONFIG_DESTDIR = pkgconfig
+	QMAKE_PKGCONFIG_LIBDIR = ${prefix}/lib
+	QMAKE_PKGCONFIG_INCDIR = ${prefix}/include
+
+	unix:QMAKE_CLEAN += -r pkgconfig lib$${TARGET}.prl
 }
 
 win32-msvc*{