Fix XFAIL tests

In commit edf0e78 I made `run-tests.sh` expect XFAIL tests to *fail*,
because I misunderstood the reason they were failing.

The tests `test_db_find_entry*` now do actually pass so they are no
longer XFAIL. It seems that clang's
`CompilationDatabase.getCompileCommands` has been fixed, as of 3.8 (at
least).

test/args.sh

@@ -64,7 +64,7 @@ test_compiler_command_line_linking_multiple_source_files_XFAIL() {
     # assembler, and linker). It means we can't generate tags for several
     # source files in a single clang-ctags invocation (except by using
     # --compile-comands).
-    ! clang-ctags -e -- -shared class.cpp overload.cpp
+    clang-ctags -e -- -shared class.cpp overload.cpp
 }
 
 test_all_headers() {

test/compile_commands.sh

@@ -17,17 +17,14 @@ test_db_with_multiple_source_files() {
     assert_vim 0 'b' b.h:1
 }
 
-test_db_find_entry_with_relative_path_XFAIL() {
-    # The lookup done by clang's CompilationDatabase.getCompileCommands (C
-    # function clang_CompilationDatabase_getCompileCommands) doesn't seem to do
-    # anything smart with the filenames, just plain string matches.
+test_db_find_entry_with_relative_path() {
     clang-ctags -e --compile-commands=compile_commands.json subdir/c.cpp
-    ! ( assert_tag c )
+    assert_tag c
 }
 
-test_db_find_entry_with_relative_path_given_absolute_path_XFAIL() {
+test_db_find_entry_with_relative_path_given_absolute_path() {
     clang-ctags -e --compile-commands=compile_commands.json "$PWD/subdir/c.cpp"
-    ! ( assert_tag c )
+    assert_tag c
 }
 
 test_db_find_entry_with_absolute_path_given_relative_path() {
@@ -41,13 +38,9 @@ test_db_find_entry_with_canonical_path_given_uncanonical_path() {
     assert_tag a
 }
 
-test_db_find_entry_relative_to_directory_XFAIL() {
-    # According to http://clang.llvm.org/docs/JSONCompilationDatabase.html
-    # the entry in compile_commands.json should be:
-    #     { "directory": "subdir", "file": "e.cpp" }
-    # i.e. with `file` relative to `directory`.
+test_db_find_entry_relative_to_directory() {
     clang-ctags -e --compile-commands=compile_commands.json subdir/e.cpp
-    ! ( assert_tag e )
+    assert_tag e
 }
 
 test_db_compile_command_from_different_directory() {