Handle case-insensitive flag names WAS Cannot resolve HDBC with time 1.4, even with flags

[hesselink]

This is similar to #396, but I can't get it to work even with flags. I can again reproduce with stack new, the following stack.yaml:

flags: {}
packages:
- '.'
extra-deps:
- HDBC-2.4.0.1
- time-1.4.2
- convertible-1.1.1.0
- utf8-string-1
flags:
  HDBC:
    minTime15: false
resolver: ghc-7.8

And adding HDBC to the build-depends of the cabal file. Issuing stack build now gives:

While constructing the BuildPlan the following exceptions were encountered:

--  Failure when adding dependencies:
      time: needed (>=1.5 && <1.6), but 1.4.2 found
    needed for package: HDBC-2.4.0.1

--  Failure when adding dependencies:
      HDBC: needed (-any), but couldn't resolve its dependencies
    needed for package: new-template-0.1.0.0

Even though, according to the cabal file in HDBC, with minTime15 on false it should depend on time < 1.5.

[hesselink]

I've figured it out: it needs to be mintime15 (without a capital t). Cabal accepts both, and the cabal file lists it with a capital t, so this is pretty confusing. Should I leave this open?

[snoyberg]

Flag names are case-insensitive? That's... surprising. Yeah, let's leave this open, I'll update the title.

[snoyberg]

@hesselink This should now be resolved on master. Could you test it out to confirm?

[hesselink]

Yes, I tried both capitalizations, and they both work. Thanks!