[libclang] API enhancements by Joe Groff!

[libclang] API enhancements by Joe Groff!

- Exposes a CXType_Vector type kind for vector types.
- Adds generalized versions of the clang_getArrayElementType and clang_getArraySize functions, named clang_getElementType and clang_getNumElements, which work on array, vector, or complex types.
- Adds additional functions for querying function types. clang_isFunctionTypeVariadic returns true if a function type is variadic. clang_getFunctionCallingConv returns an enumeration value indicating the calling convention of the function type. clang_getNumArgTypes returns the number of static argument types, and clang_getArgType gets the type of an argument.
- Adds a clang_getTypedefDeclUnderlyingType function to get the underlying type from a TypedefDecl cursor.
- Adds a clang_getEnumDeclIntegerType function to get the integer type from an EnumDecl cursor.
- Adds clang_getEnumConstantDeclValue and clang_getEnumConstantDeclUnsignedValue functions to get the value of an EnumConstantDecl as a signed or unsigned long long, respectively.
- Exposes a CXCursor_AsmLabelAttr cursor kind for __asm__("label") attributes.
- Alters clang_getCursorSpelling to return the label value for AsmLabelAttr-kind cursors.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@145972 91177308-0d34-0410-b5e6-96231b3b80d8