configure.ac error in VCVER use and in firebird mac exclusion

Change-Id: If63c8b8a4d2f51426d0b7caacd14b985e53eb441
Reviewed-on: https://gerrit.libreoffice.org/19674Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>
Tested-by: Norbert Thiebaud <nthiebaud@gmail.com>

configure.ac

@@ -8107,7 +8107,7 @@ internal)
     # On windows we are supporting two different python versions: 3.3 and 3.5.
     # We msut do it as long as we support MSVC 2013. Python 3.3 can be removed
     # when MSVC 2013 support was dropped.
-    if test "$COM" = "MSC" -a $VCVER = 120; then
+    if test "$COM" = "MSC" -a "$VCVER" = "120"; then
         PYTHON_VERSION_MINOR=3
     else
         PYTHON_VERSION_MINOR=5
@@ -8514,7 +8514,7 @@ dnl Check for Firebird stuff
 dnl ===================================================================
 ENABLE_FIREBIRD_SDBC=""
 if test -z "$enable_firebird_sdbc" ; then
-    if test "$_os" = "Darwin" -a "$MACOSX_SDK_VERSION" -ge 101100 ; then
+    if test "$_os" = "Darwin" -a ${MACOSX_SDK_VERSION:-0} -ge 101100 ; then
         AC_MSG_NOTICE([firebird does not build on 10.11.. default to --disable-firebird-sdbc ])
         enable_firebird_sdbc="no"
     else