layers: Fix extension func/core struct codegen

Fix code generation for extension functions receiving struct parameter
types defined by core Vulkan.  Extensions are processed as separate
features by the code generator, and the type info required for structure
generation was not being shared across features.  The code generator has
been modified to share type info across features so that the validation
code generated for extension functions includes validation for core
structures:
 - Prevent unique objects and parameter validation code generators from
   clearing struct type info data structures at the start of feature
   processing.
 - Remove unused data structures from unique objects code generator.
 - Adds handle unwrapping and parameter validation for elements in the
   vkCmdPushDescriptorSetKHR pDescriptorWrites parameter.
 - Adds handle unwrapping and parameter validation for elements in the
   vkCreateSharedSwapCHainsKHR pCreateInfos parameter.
 - Adds VkAllocationCallback parameter validation to the WSI and
   descriptor update template extensions functions.

Change-Id: I016aa6550681dbf7d6bda834272374ce63ed1940
diff --git a/scripts/unique_objects_generator.py b/scripts/unique_objects_generator.py
index a6dae64..1773c3b 100644
--- a/scripts/unique_objects_generator.py
+++ b/scripts/unique_objects_generator.py
@@ -136,6 +136,7 @@
             'vkCreateComputePipelines',
             'vkCreateGraphicsPipelines',
             'vkCreateSwapchainKHR',
+            'vkCreateSharedSwapchainsKHR',
             'vkGetSwapchainImagesKHR',
             'vkEnumerateInstanceLayerProperties',
             'vkEnumerateDeviceLayerProperties',
@@ -162,16 +163,9 @@
         self.headerVersion = None
         # Internal state - accumulators for different inner block text
         self.sections = dict([(section, []) for section in self.ALL_SECTIONS])
-        self.structNames = []                             # List of Vulkan struct typenames
-        self.structTypes = dict()                         # Map of Vulkan struct typename to required VkStructureType
-        self.handleTypes = set()                          # Set of handle type names
-        self.commands = []                                # List of CommandData records for all Vulkan commands
         self.structMembers = []                           # List of StructMemberData records for all Vulkan structs
-        self.flags = set()                                # Map of flags typenames
         # Named tuples to store struct and command data
-        self.StructType = namedtuple('StructType', ['name', 'value'])
         self.CommandParam = namedtuple('CommandParam', ['type', 'name', 'ispointer', 'isconst', 'iscount', 'len', 'extstructs', 'cdecl', 'islocal', 'iscreate', 'isdestroy'])
-        self.CommandData = namedtuple('CommandData', ['name', 'return_type', 'params', 'cdecl'])
         self.StructMemberData = namedtuple('StructMemberData', ['name', 'members'])
     #
     def incIndent(self, indent):
@@ -236,14 +230,7 @@
         OutputGenerator.beginFeature(self, interface, emit)
         self.headerVersion = None
         self.sections = dict([(section, []) for section in self.ALL_SECTIONS])
-        self.structNames = []
-        self.structTypes = dict()
-        self.handleTypes = set()
-        self.commands = []
-        self.structMembers = []
         self.cmdMembers = []
-        self.flags = set()
-        self.StructMemberData = namedtuple('StructMemberData', ['name', 'members'])
         self.CmdMemberData = namedtuple('CmdMemberData', ['name', 'members'])
         if self.featureName != 'VK_VERSION_1_0':
             white_list_entry = []
@@ -284,7 +271,6 @@
         # Otherwise, emit the tag text.
         category = typeElem.get('category')
         if (category == 'struct' or category == 'union'):
-            self.structNames.append(name)
             self.genStruct(typeinfo, name)
     #
     # Append a definition to the specified section
@@ -383,8 +369,6 @@
                     value = result.group(0)
                 else:
                     value = self.genVkStructureType(typeName)
-                # Store the required type value
-                self.structTypes[typeName] = self.StructType(name=name, value=value)
             # Store pointer/array/string info
             membersInfo.append(self.CommandParam(type=type,
                                                  name=name,