build,qt: Explicitly namespace a few Qt variables for Qt5

m4/qt.m4: Rename to
m4/qt5.m4: this.
(FIND_QT): Rename to FIND_QT5.
(GPGME_QT): Change variable prefix to GPGME_QT5.
(GPGME_QTTEST: Change variable prefix to GPGME_QT5TEST.
configure.ac, lang/qt/src/Makefile.am, lang/qt/tests/Makefile.am:
Adjust accordingly.
--

In preparation to adding support for building qgpgme for Qt6, add the
version number to a few variables to avoid confusion.

configure.ac

@@ -375,7 +375,7 @@ if test "$found" = "1"; then
 *** Qt language binding depends on cpp binding.
 ***]])
     fi
-    FIND_QT
+    FIND_QT5
     if test "$have_qt5_libs" != "yes"; then
         if test "$explicit_languages" = "1"; then
         AC_MSG_ERROR([[
@@ -408,7 +408,7 @@ LIST_MEMBER("qt", $enabled_languages)
 if test "$found" = "1"; then
     AX_GCC_FUNC_ATTRIBUTE(visibility)
     if test "$ax_cv_have_func_attribute_visibility" = "yes"; then
-        GPGME_QT_CFLAGS="$GPGME_QT_CFLAGS -fvisibility=hidden"
+        GPGME_QT5_CFLAGS="$GPGME_QT5_CFLAGS -fvisibility=hidden"
     fi
 fi
 

lang/qt/src/Makefile.am

@@ -261,12 +261,12 @@ nodist_qgpgmeinclude_HEADERS = qgpgme_version.h
 libqgpgme_la_SOURCES = $(qgpgme_sources) $(qgpgme_headers) $(private_qgpgme_headers)
 
 AM_CPPFLAGS = -I$(top_srcdir)/lang/cpp/src -I$(top_builddir)/src \
-              @GPGME_QT_CFLAGS@ @GPG_ERROR_CFLAGS@ @LIBASSUAN_CFLAGS@ \
+              @GPGME_QT5_CFLAGS@ @GPG_ERROR_CFLAGS@ @LIBASSUAN_CFLAGS@ \
               -DBUILDING_QGPGME -Wsuggest-override \
               -Wzero-as-null-pointer-constant
 
 libqgpgme_la_LIBADD = ../../cpp/src/libgpgmepp.la ../../../src/libgpgme.la \
-                       @LIBASSUAN_LIBS@ @GPG_ERROR_LIBS@ @GPGME_QT_LIBS@
+                       @LIBASSUAN_LIBS@ @GPG_ERROR_LIBS@ @GPGME_QT5_LIBS@
 libqgpgme_la_LDFLAGS = -no-undefined -version-info \
     @LIBQGPGME_LT_CURRENT@:@LIBQGPGME_LT_REVISION@:@LIBQGPGME_LT_AGE@
 

lang/qt/tests/Makefile.am

@@ -45,12 +45,12 @@ moc_files = \
 AM_LDFLAGS = -no-install
 
 LDADD = ../../cpp/src/libgpgmepp.la ../src/libqgpgme.la \
-        ../../../src/libgpgme.la @GPGME_QT_LIBS@ @GPG_ERROR_LIBS@ \
-        @GPGME_QTTEST_LIBS@ @LDADD_FOR_TESTS_KLUDGE@ -lstdc++
+        ../../../src/libgpgme.la @GPGME_QT5_LIBS@ @GPG_ERROR_LIBS@ \
+        @GPGME_QT5TEST_LIBS@ @LDADD_FOR_TESTS_KLUDGE@ -lstdc++
 
 AM_CPPFLAGS = -I$(top_srcdir)/lang/cpp/src -I$(top_builddir)/src \
-              @GPG_ERROR_CFLAGS@ @GPGME_QT_CFLAGS@ @GPG_ERROR_CFLAGS@ \
-              @LIBASSUAN_CFLAGS@ @GPGME_QTTEST_CFLAGS@ -DBUILDING_QGPGME \
+              @GPG_ERROR_CFLAGS@ @GPGME_QT5_CFLAGS@ @GPG_ERROR_CFLAGS@ \
+              @LIBASSUAN_CFLAGS@ @GPGME_QT5TEST_CFLAGS@ -DBUILDING_QGPGME \
               -I$(top_srcdir)/lang/qt/src \
               -DTOP_SRCDIR="$(top_srcdir)"
 

m4/qt5.m4

@@ -1,31 +1,31 @@
-dnl qt.m4
+dnl qt5.m4
 dnl Copyright (C) 2016 Intevation GmbH
 dnl
 dnl This file is part of gpgme and is provided under the same license as gpgme
 
-dnl Autoconf macro to find either Qt4 or Qt5
+dnl Autoconf macro to find Qt5
 dnl
-dnl sets GPGME_QT_LIBS and GPGME_QT_CFLAGS
+dnl sets GPGME_QT5_LIBS and GPGME_QT5_CFLAGS
 dnl
 dnl if QT5 was found have_qt5_libs is set to yes
 
-AC_DEFUN([FIND_QT],
+AC_DEFUN([FIND_QT5],
 [
   have_qt5_libs="no";
 
-  PKG_CHECK_MODULES(GPGME_QT,
+  PKG_CHECK_MODULES(GPGME_QT5,
                     Qt5Core >= 5.0.0,
                     [have_qt5_libs="yes"],
                     [have_qt5_libs="no"])
 
-  PKG_CHECK_MODULES(GPGME_QTTEST,
+  PKG_CHECK_MODULES(GPGME_QT5TEST,
                     Qt5Test >= 5.0.0,
                     [have_qt5test_libs="yes"],
                     [have_qt5test_libs="no"])
 
   if ! test "$have_w32_system" = yes; then
     if "$PKG_CONFIG" --variable qt_config Qt5Core | grep -q "reduce_relocations"; then
-      GPGME_QT_CFLAGS="$GPGME_QT_CFLAGS -fpic"
+      GPGME_QT5_CFLAGS="$GPGME_QT5_CFLAGS -fpic"
     fi
   fi
   if test "$have_qt5_libs" = "yes"; then
@@ -61,9 +61,9 @@ AC_DEFUN([FIND_QT],
     dnl we check here that we can actually compile / link a qt application
     dnl for host.
     OLDCPPFLAGS=$CPPFLAGS
-    CPPFLAGS=$GPGME_QT_CFLAGS
+    CPPFLAGS=$GPGME_QT5_CFLAGS
     OLDLIBS=$LIBS
-    LIBS=$GPGME_QT_LIBS
+    LIBS=$GPGME_QT5_LIBS
     AC_LANG_PUSH(C++)
     AC_MSG_CHECKING([whether a simple qt program can be built])
     AC_LINK_IFELSE([AC_LANG_SOURCE([