contrib: assume OS X 10.7 by default and raise compatibility level to 10.6

contrib/bootstrap

@@ -143,7 +143,7 @@ add_make_enabled()
 
 check_macosx_sdk()
 {
-   [ -z "${OSX_VERSION}" ] && echo "OSX_VERSION not specified, assuming 10.6" && OSX_VERSION=10.6
+   [ -z "${OSX_VERSION}" ] && echo "OSX_VERSION not specified, assuming 10.7" && OSX_VERSION=10.7
    if test -z "$SDKROOT"
    then
       SDKROOT=`xcode-select -print-path`/Platforms/MacOSX.platform/Developer/SDKs/MacOSX$OSX_VERSION.sdk

contrib/src/main.mak

@@ -105,7 +105,7 @@ CXX := $(HOST)-g++ --sysroot=$(ANDROID_NDK)/platforms/android-9/arch-$(PLATFORM_
 endif
 
 ifdef HAVE_MACOSX
-MIN_OSX_VERSION=10.5
+MIN_OSX_VERSION=10.6
 CC=gcc-4.2
 CXX=g++-4.2
 AR=ar