import from LLVM 21.1.8

fix `after/syntax/llvm.vim` is loaded even if `g:llvm_extends_official` is set

import from LLVM 19.1.0

import from LLVM 16.0.4

follow upstream LLVM 15.0.7

import updates from tags/llvmorg-15.0.0 (4ba6a9c9f65bbc8bd06e3652cb20fd4dfc846137)

sync with LLVM 14.0.3

import from LLVM 12.0.0

ensure to delete temporary file on error

fix lint warning and better regex

simplify condition to detect 'llvm' filetype from buffer

update README following imports from LLVM 11.1.0

import mlir/utils/vim from tags/llvmorg-11.1.0 (1fdec59bffc11ae37eb51a1b9869f0696bfd5312)

import updates from tags/llvmorg-11.1.0 (1fdec59bffc11ae37eb51a1b9869f0696bfd5312)

tweak installation section