Makefile colorization: fix old issues and improvement (~4 changes)

[fadeevab]

1. This pull request fixes the following issue: Makefile parsing bug? #25469
2. Additional improvements according to Makefile documentation.

Before:

After:

Total list of changes at the moment:

1. Allow spaces before ifeq, define, endif, ended, else.
2. Handle braces properly inside the variable, e.g. $(info ()()(())).
3. Handle backslash inside end-of-line inside the $(variable).
4. Handle $$ and special variables according to Makefile documentation.

[msftclas]

@fadeevab,
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[fadeevab]

@aeschli Pull request to textmate is updated as well (textmate/make.tmbundle#15)

[aeschli]

Thanks @fadeevab . I will update the grammar next week (we're currently in the end game week).

[aeschli]

BTW, no need to make a PR. It's also good enough if you file me an issue and ask to to run the update script

[msftclas]

@fadeevab, thanks for signing the contribution license agreement. We will now validate the agreement and then the pull request.

Thanks, Microsoft Pull Request Bot

[fadeevab]

I added commits and test cases. But I didn't ported them to TextMate yet. Wait until I update TextMate. The reason is that I develop in VSCode firstly. It's unreal to develop in XML format initially.

[fadeevab]

@aeschli , FYI, TextMate xml is updated, you can check here the test

[fadeevab]

@aeschli You can check it now.

Total list of changes at the moment:

1. Allow spaces before ifeq, define, endif, ended, else.
2. Handle braces properly inside the variable, e.g. $(info ()()(())).
3. Handle backslash inside end-of-line inside the $(variable).
4. Handle $$ and special variables according to Makefile documentation.

I didn't updated the latest expected result according to the new test, thus the latest build failed.

[aeschli]

Closing the PR. We are in sync with https://github.com/fadeevab/make.tmbundle

[fadeevab]

Thank you!