Fixed ugly workaround for compiler detection

Corrected ugly workaround for compiler detection in code with
correct definition in llpreprocessor.h and updated various #if
to reflect this.

indra/llcommon/llhash.h

@@ -39,17 +39,13 @@
 #include <hash_map>
 #include <algorithm>
 #elif LL_DARWIN || LL_LINUX
-#if CC_GCC || CC_ICC
-#  if GCC_VERSION >= 40300 || CC_ICC// gcc 4.3 or icc 11 and up
-#    include <backward/hashtable.h>
-#  elif GCC_VERSION >= 30400 // gcc 3.4 and up
-#    include <ext/hashtable.h>
-#  elif __GNUC__ >= 3
-#    include <ext/stl_hashtable.h>
-#  else
-#    include <hashtable.h>
-#  endif
-#elif CC_CLANG
+#if GCC_VERSION >= 40300 || LL_ICC// gcc 4.3 or icc 11 and up
+#  include <backward/hashtable.h> 
+#elif GCC_VERSION >= 30400 // gcc 3.4 and up
+#  include <ext/hashtable.h>
+#elif __GNUC__ >= 3
+#  include <ext/stl_hashtable.h>
+#else
 #  include <hashtable.h>
 #endif
 #elif LL_SOLARIS

indra/llcommon/llpreprocessor.h

@@ -78,7 +78,18 @@
 
 
 // Figure out differences between compilers
-#if defined(__GNUC__)
+#if defined(__clang__) && defined(__GNUC__)
+	#define CLANG_VERSION (__clang_major__ * 10000 \
+						+ __clang_minor__ * 100 \
+						+ __clang_patchlevel__)
+	#ifndef LL_CLANG
+		#define LL_CLANG 1
+	#endif
+#elif defined (__ICC) && defined(__GNUC__)
+	#ifndef LL_ICC
+		#define LL_ICC 1
+	#endif
+#elif defined(__GNUC__)
 	#define GCC_VERSION (__GNUC__ * 10000 \
 						+ __GNUC_MINOR__ * 100 \
 						+ __GNUC_PATCHLEVEL__)

indra/llcommon/llprocessor.cpp

@@ -55,10 +55,10 @@
 #      define LL_X86 1
 #elif LL_MSVC && _M_IX86
 #      define LL_X86 1
-#elif LL_GNUC && ( defined(__amd64__) || defined(__x86_64__) )
+#elif LL_GNUC || LL_ICC || LL_CLANG && ( defined(__amd64__) || defined(__x86_64__) )
 #      define LL_X86_64 1
 #      define LL_X86 1
-#elif LL_GNUC && ( defined(__i386__) )
+#elif LL_GNUC || LL_ICC || LL_CLANG && ( defined(__i386__) )
 #      define LL_X86 1
 #elif LL_GNUC && ( defined(__powerpc__) || defined(__ppc__) )
 #      define LL_PPC 1