layers: Improved generated struct validation code
layers: Improved generated struct validation code

Improvements to the parameter validation code generator, primarily to
eliminate string concatenations performed when processing structs.  A
validation function was being produced for each struct, which received a
string specifying the name of the struct parameter.  This string was then
concatenated with the names of the struct members.  The struct validation
code is no longer in a separate function, and a single string containing
the full names of each struct member (eg. pCreateInfo->pApplicationInfo)
is created at code generation time.

Change-Id: I2800bfbc26247e4e4c6f8c885c0e7c4b8b3776a2

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools