Bug 1248534 (part 1) - Remove XPT encoding support. r=khuey.

Currently XPT can both encode and decode, but encoding has been handled by
Python code since bug 643817, so the encoding support can be removed. This
results in many simplifications. Some notable changes:

- All the XPTHashTable code (including XPTDatapool::offset_map) is no longer
  necessary.

- PrimitiveTest.cpp and SimpleTypeLib.cpp both don't make much sense without
  encoding support, so I removed them.

- A lot of the version code was already unused, e.g. XPT_VERSION_*,
  XPT_TYPELIB_VERSIONS_STRUCT, XPT_TYPELIB_VERSIONS.
  XPT_MAJOR_INCOMPATIBLE_VERSION is the only thing actually used in version
  checks.

- The patch also removes some code that was dead even before encoding removal,
  such as XPT_ParseVersionString().

xpcom/moz.build

@@ -32,7 +32,6 @@ if CONFIG['OS_ARCH'] == 'WINNT' and CONFIG['MOZ_DEBUG']:
 
 TEST_DIRS += [
     'tests',
-    'typelib/xpt/tests',
 ]
 
 #  Can't build internal xptcall tests that use symbols which are not exported.

xpcom/reflect/xptinfo/xptiInterfaceInfoManager.cpp

@@ -99,7 +99,7 @@ XPTInterfaceInfoManager::InitMemoryReporter()
 void
 XPTInterfaceInfoManager::RegisterBuffer(char *buf, uint32_t length)
 {
-    XPTState *state = XPT_NewXDRState(XPT_DECODE, buf, length);
+    XPTState *state = XPT_NewXDRState(buf, length);
     if (!state)
         return;