Only allocate a copy of style strings if requested.

[Quipyowert2]

do_free_src_and_alloc_copy wasn't being checked for the placement
position, the initial map command, the title format, and the icon title
format.

Fixes #430.

• What does this PR do?
  I took a different approach to fixing 21 byte memory leak in merge_styles (3 tiny leaks of 7 bytes) #430. This pull request fixes 21 byte memory leak in merge_styles (3 tiny leaks of 7 bytes) #430 by only allocating a copy of the style strings if copying was requested (i.e. do_free_src_and_alloc_copy is True), instead of the Fix a 21 byte memory leak. #431 approach that involved trying to free the style, which broke setting icon images.

I hope this PR doesn't break anything like my previous one did.

• Screenshots (if applicable)

• PR acceptance criteria (reminder only, please delete once read)

  • Your commit message(s) are descriptive. See:

    https://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html

  • [https://raw.githubusercontent.com/fvwmorg/fvwm3/master/doc/README]Documentation updated (where appropriate)

  • Style guide followed (try and match the surrounding code where possible)

  • All tests are passing: although this is automatic, Codacy will often
    highlight additional considerations which will need to be addressed before
    the PR can be merged.

• Issue number(s)

If this PR addresses any issues, please ensure the appropriate commit
message(s) contains:

Fixes #XXX

at the end of your commit message, where XXX should be replaced with the
relevant issue number.

If there is more than one issue fixed then use:

Fixes #XXX, fixes #YYY, fixes #ZZZ

[ThomasAdam]

Hi @Quipyowert2

Thanks. This looks correct, I'll take a proper look later on today. Although it's not related to your change per se, I absolutely dislike the pattern of heap vs stack, just because of state elsewhere. It's absolutely awful, but will get fixed over time...