OS/2 + Windows: Don't build KDE/Gnome password plugins.

OS/2: Correctly link to libcrypto
BUILDING: Make a note about gdb being requirement for debug build

BUILDING

@@ -45,6 +45,8 @@ Linux / Unix
      - kdelibs-dev installed
      - set KDE_INTEGRATION build flag
 
+  For debug build, gdb is required by qmake.
+
 MAC OS X
 ----------------------------------------------------------------------------------
 

src/lib/lib.pro

@@ -521,7 +521,7 @@ win32 {
 }
 
 os2 {
-    LIBS += -llibeay32
+    LIBS += -lcrypto
 }
 
 mac {

src/plugins/plugins.pro

@@ -9,7 +9,7 @@ defineTest(addSubdir) {
             fullPath = $$replace(entry, ;,"")
             fullPath = $$replace(fullPath, \\\\, /)
             name = $$replace(fullPath, $$re_escape("$$subdir/"), "")
-            win32: fullPath = $$lower($$fullPath)
+            os2|win32: fullPath = $$lower($$fullPath)
             exists($$fullPath/*.pro): SUBDIRS += $$fullPath
         }
     }
@@ -17,23 +17,23 @@ defineTest(addSubdir) {
     export (SUBDIRS)
 }
 
+defineTest(disablePlugin) {
+    SUBDIRS -= $$PWD/$$1
+    os2|win32: SUBDIRS -= $$lower($$PWD/$$1)
+
+    export(SUBDIRS)
+}
+
 addSubdir($$PWD)
 
 outOfDirPlugins = $$(QUPZILLA_PLUGINS_SRCDIR)
-!equals(outOfDirPlugins, "") : addSubdir($$(QUPZILLA_PLUGINS_SRCDIR))
+!equals(outOfDirPlugins, ""): addSubdir($$(QUPZILLA_PLUGINS_SRCDIR))
 
 # TestPlugin only in debug build
-!CONFIG(debug, debug|release): SUBDIRS -= $$PWD/TestPlugin
+!CONFIG(debug, debug|release): disablePlugin(TestPlugin)
 
 # KWalletPasswords only with KDE_INTEGRATION
-!contains(DEFINES, KDE_INTEGRATION): SUBDIRS -= $$PWD/KWalletPasswords
-!lessThan(QT_VERSION, 5.0): SUBDIRS -= $$PWD/KWalletPasswords
+!contains(DEFINES, KDE_INTEGRATION) | equals(QT_MAJOR_VERSION, 5): disablePlugin(KWalletPasswords)
 
 # GnomeKeyringPasswords only with GNOME_INTEGRATION
-!contains(DEFINES, GNOME_INTEGRATION): SUBDIRS -= $$PWD/GnomeKeyringPasswords
-!system(pkg-config --exists gnome-keyring-1): SUBDIRS -= $$PWD/GnomeKeyringPasswords
-
-!unix|mac {
-    SUBDIRS -= $$lower($$PWD/KWalletPasswords)
-    SUBDIRS -= $$lower($$PWD/GnomeKeyringPasswords)
-}
+!contains(DEFINES, GNOME_INTEGRATION) | !system(pkg-config --exists gnome-keyring-1): disablePlugin(GnomeKeyringPasswords)