Support commented out lines in the PATCHES section.

[OscarL]

We could have commented out lines in PROVIDES, and REQUIRES, but not in PATCHES, as those lines weren't being filtered out, ending on "file not found" errors further down.

[OscarL]

Some examples, to explain what I'm after....

Currently we can have:

PROVIDES="
    super_app
    cmd:awesome_bin
#    cmd:leaving_this_out_for_now
    "

or:

REQUIRES="
    haiku
    lib:libwhatever
#    lib:might_need_this_one_depending_on_build_options
    "

This PR add support for doing similar, but on PATCHES, as in:

PATCHES="
    main.patchset
#    optional_patch_from_debian.diff
    another_patch_from_debian.patch
    "

Currently, the latter just errors out. Not a biggie, but I think being consistent on allowing commented lines in multi-lines blocks is nice.

[Begasus]

A little background on the merge from my side, I tend to grab patches (or search them) from other resources, check them out and sometimes they don't apply, I always had to remove the mentioned line to continue.
This is especialy handy for these things, not specific to buildmasters. Thanks @OscarL !