Add missing export. Spotted by Leandro Melo.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@143508 91177308-0d34-0410-b5e6-96231b3b80d8

tools/libclang/libclang.exports

@@ -92,6 +92,7 @@ clang_getDiagnosticOption
 clang_getDiagnosticRange
 clang_getDiagnosticSeverity
 clang_getDiagnosticSpelling
+clang_getExpansionLocation
 clang_getFile
 clang_getFileName
 clang_getFileTime