Add Imagination Technologies to the vendors in llvm::Triple

[dsanders]

Summary

This is a pre-requisite for supporting the mips-img-linux-gnu triple in clang.

[atanasyan]

LGTM

include/llvm/ADT/Triple.h

enum VendorType {
 
     Apple,
     PC,
     SCEI,
     BGP,
     BGQ,
     Freescale,
     IBM,
+    ImaginationTechnologies,
     NVIDIA
   };
   enum OSType {
     UnknownOS,
 
     AuroraUX,
     Cygwin,
     Darwin,

lib/Support/Triple.cpp

const char *Triple::getVendorTypeName(VendorType Kind) {
 
   case Apple: return "apple";
   case PC: return "pc";
   case SCEI: return "scei";
   case BGP: return "bgp";
   case BGQ: return "bgq";
   case Freescale: return "fsl";
   case IBM: return "ibm";
+  case ImaginationTechnologies: return "img";
   case NVIDIA: return "nvidia";
   }
 
   llvm_unreachable("Invalid VendorType!");
 }
 
 const char *Triple::getOSTypeName(OSType Kind) {
   switch (Kind) {
static Triple::VendorType parseVendor(StringRef VendorName) {
   return StringSwitch<Triple::VendorType>(VendorName)
     .Case("apple", Triple::Apple)
     .Case("pc", Triple::PC)
     .Case("scei", Triple::SCEI)
     .Case("bgp", Triple::BGP)
     .Case("bgq", Triple::BGQ)
     .Case("fsl", Triple::Freescale)
     .Case("ibm", Triple::IBM)
+    .Case("img", Triple::ImaginationTechnologies)
     .Case("nvidia", Triple::NVIDIA)
     .Default(Triple::UnknownVendor);
 }
 
 static Triple::OSType parseOS(StringRef OSName) {
   return StringSwitch<Triple::OSType>(OSName)
     .StartsWith("auroraux", Triple::AuroraUX)
     .StartsWith("cygwin", Triple::Cygwin)