Upgrade to GCC 4.8 for Linux standalone build.

This patch modifies android-configure.sh to use the prebuilt 4.8
Linux host toolchain when available.

+ Fix a few sources to get rid of ugly compiler warnings.

Note: this works best with the following patch for the GPU
      emulation libraries:

      https://android-review.googlesource.com/#/c/92482/1

Change-Id: I7ae1c6cf2d58c2902affa36886bfa87956da622d
diff --git a/android-configure.sh b/android-configure.sh
index d28209a..65f08c5 100755
--- a/android-configure.sh
+++ b/android-configure.sh
@@ -104,11 +104,15 @@
 fi
 
 # On Linux, try to use our prebuilt toolchain to generate binaries
-# that are compatible with Ubuntu 8.04
+# that are compatible with Ubuntu 10.4
 if [ -z "$CC" -a -z "$OPTION_CC" -a "$HOST_OS" = linux ] ; then
-    PROBE_HOST_CC=`dirname $0`/../../prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.11-4.6/bin/x86_64-linux-gcc
-    if [ ! -f "$PROBE_HOST_CC" ] ; then
-        PROBE_HOST_CC=`dirname $0`/../../prebuilts/tools/gcc-sdk/gcc
+    PREBUILTS_HOST_GCC=$(dirname $0)/../../prebuilts/gcc/linux-x86/host
+    PROBE_HOST_CC=$PREBUILTS_HOST_GCC/x86_64-linux-glibc2.11-4.8/bin/x86_64-linux-gcc
+    if [ ! -f "$PROBE_HOST_CC" ]; then
+        PROBE_HOST_CC=$PREBUILTS_HOST_GCC/x86_64-linux-glibc2.11-4.6/bin/x86_64-linux-gcc
+        if [ ! -f "$PROBE_HOST_CC" ] ; then
+            PROBE_HOST_CC=$(dirname $0)/../../prebuilts/tools/gcc-sdk/gcc
+        fi
     fi
     if [ -f "$PROBE_HOST_CC" ] ; then
         echo "Using prebuilt toolchain: $PROBE_HOST_CC"