vim: add swiftcc keyword

Update the syntax highlighting for SVN r265480.

llvm-svn: 266705
diff --git a/llvm/utils/vim/syntax/llvm.vim b/llvm/utils/vim/syntax/llvm.vim
index 403760b..a9c12e2 100644
--- a/llvm/utils/vim/syntax/llvm.vim
+++ b/llvm/utils/vim/syntax/llvm.vim
@@ -53,9 +53,9 @@
 syn keyword llvmKeyword readonly release returns_twice sanitize_thread
 syn keyword llvmKeyword sanitize_memory section seq_cst sideeffect signext
 syn keyword llvmKeyword singlethread source_filename spir_func spir_kernel sret
-syn keyword llvmKeyword ssp sspreq sspstrong tail target thread_local to triple
-syn keyword llvmKeyword unnamed_addr unordered uwtable volatile weak weak_odr
-syn keyword llvmKeyword x86_fastcallcc x86_stdcallcc x86_thiscallcc
+syn keyword llvmKeyword ssp sspreq sspstrong swiftcc tail target thread_local to
+syn keyword llvmKeyword triple unnamed_addr unordered uwtable volatile weak
+syn keyword llvmKeyword weak_odr x86_fastcallcc x86_stdcallcc x86_thiscallcc
 syn keyword llvmKeyword x86_64_sysvcc x86_64_win64cc zeroext uselistorder
 syn keyword llvmKeyword uselistorder_bb musttail