Bump Objective-C runtime version and add installation instructions

Author: hmelder

INSTALL

@@ -20,7 +20,10 @@ particular operating system and CPU. These instructions come with the
 GNUstep-HOWTO and are also located at the GNUstep web site at
 <http://www.gnustep.org>.
 
-   Quick installation instructions:
+1.1.1 Quick Installation Instructions
+---------------------
+
+To build and install the GNUstep Makefiles, run the following commands:
 
      ./configure
      make
@@ -44,6 +47,27 @@ filesystem layout).
      make
      make install
 
+1.1.2 Enabling Modern Objective-C Features
+---------------------
+
+GNUstep supports the legacy GCC runtime, and the modern libobjc2 runtime with
+Objective-C 2.0 Features such as ARC, Blocks (closures),  Synthesised property
+accessors, Efficient support for @synchronized() and more.
+
+   libobjc2 requires building with clang. If you've installed both clang and libobjc2
+you can configure GNUstep Make to use the newer runtime and features.
+Here is an example with the runtime version set to 2.2.
+(Set it to the last libobjc2 version to benefit from possible changes in Clang CodeGen).
+Please note that we explicitly enable some features such as objc-arc that might
+be infered from the runtime version.
+
+      ./configure
+		  --enable-native-objc-exceptions \
+  		  --enable-objc-arc \
+  		  --with-runtime-abi=gnustep-2.2 \
+  		  --with-library-combo=ng-gnu-gnu \
+  	CC="clang" CXX="clang++" CPP="clang -E" LDFLAGS="-fuse-ld=lld"
+
 1.2 Configuration
 =================
 

configure.ac

@@ -1298,7 +1298,7 @@ if test x"$USE_ARC" = x"yes"; then
   # What we want to do: set USE_ARC to yes if we can compile
   # something with -fobjc-arc.
   CFLAGS_no_arc="$CFLAGS"
-  CFLAGS="$CFLAGS -fobjc-runtime=gnustep-1.8 -fobjc-arc"
+  CFLAGS="$CFLAGS -fobjc-runtime=gnustep-2.2 -fobjc-arc"
   AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
 /* Note that we never execute this code so it does not really matter
    what it is.  We are testing that the compiler accepts the

library-combo.make

@@ -47,7 +47,7 @@ ifeq ($(OBJC_RUNTIME_LIB), ng)
     ifneq ($(DEFAULT_OBJC_RUNTIME_ABI),)
       RUNTIME_VERSION=$(DEFAULT_OBJC_RUNTIME_ABI)
    else
-     RUNTIME_VERSION=gnustep-1.8
+     RUNTIME_VERSION=gnustep-2.2
    endif
   endif
   RUNTIME_FLAG = -fobjc-runtime=$(RUNTIME_VERSION) -fblocks

m4/gs_objc_runtime.m4

@@ -254,7 +254,7 @@ AC_DEFUN([GS_CHECK_OBJC_RUNTIME], [
 ])
 
 
-# Helper macro for checking gnustep-2.0 ABI support in libobjc via the __objc_load macro
+# Helper macro for checking gnustep-2.x ABI support in libobjc via the __objc_load macro
 AC_DEFUN([_GS_HAVE_OBJC_LOAD], [
     AC_REQUIRE([GS_CHECK_OBJC_RUNTIME])
     AC_CHECK_FUNC([__objc_load])
@@ -266,11 +266,11 @@ AC_DEFUN([_GS_HAVE_OBJC_LOAD], [
 #
 # DESCRIPTION
 # 
-# Checks for support for the gnustep-2.0 ABI in the runtime library. Sets the `libobjc_SUPPORTS_ABI20' variable.
+# Checks for support for the gnustep-2.x ABI in the runtime library. Sets the `libobjc_SUPPORTS_ABI20' variable.
 AC_DEFUN([GS_CHECK_RUNTIME_ABI20_SUPPORT], [
     AC_REQUIRE([GS_CHECK_OBJC_RUNTIME])
     AC_REQUIRE([_GS_HAVE_OBJC_LOAD])
-    AC_CACHE_CHECK([whether runtime library supports the gnustep-2.0 ABI],
+    AC_CACHE_CHECK([whether runtime library supports the gnustep-2.x ABI],
         [gs_cv_libobjc_abi_20], [
             if test x"$libobjc_SUPPORTS_ABI20" = x""; then
                 gs_cv_libobjc_abi_20=$ac_cv_func___objc_load

m4/gs_runtime_abi.m4

@@ -13,13 +13,13 @@ AC_DEFUN([GS_RUNTIME_ABI],dnl
    AC_REQUIRE([GS_CHECK_GCC_VERSION])
    case "$OBJC_RUNTIME_LIB" in
         gnu) default_runtime_abi=gcc         ;;
-        ng)  default_runtime_abi=gnustep-1.8 ;;
+        ng)  default_runtime_abi=gnustep-2.2 ;;
         *)   default_runtime_abi="(unknown)" ;;
     esac
     if test ! x"$1" = x""; then
         default_runtime_abi="$1"
     elif test x"$OBJC_RUNTIME_LIB" = x"ng" -a x"$libobjc_SUPPORTS_ABI20" = x"yes" -a x"$CLANG_CC" = x"yes" -a "${gs_cv_gcc_major_version}" -ge "8"; then
-        default_runtime_abi=gnustep-2.0
+        default_runtime_abi=gnustep-2.2
     fi
     AC_ARG_WITH([runtime-abi],
         [AS_HELP_STRING([--with-runtime-abi], [