Delete cabal.project (#613)

* Delete cabal.project

It seems to no longer do anything useful, and it also prevents
CI from detecting that include/bytestring-cpp-macros.h
was not getting picked up by `cabal sdist`.

* Add bytestring-cpp-macros.h to install-includes

In particular, this ensures that `cabal sdist` grabs it.

* Add bytestring-cpp-macros.h to includes

The cabal documentation claims as a pre-requisite for its
usability "when compiling the package itself."  It's unclear
if this is really true, but there is no harm done in adding
bytestring-cpp-macros.h there just in case.

* Experiment: When is __ARM_FEATURE_UNALIGNED visible?

* Remove __ARM_FEATURE_UNALIGNED experiment/warnings

It seems this macro is never visible in Haskell code.
But with real unaligned primops in the near future,
it doesn't seem worth messing with.

Author: clyring

bytestring.cabal

@@ -66,7 +66,7 @@ Tested-With:         GHC==9.4.1,
                      GHC==8.0.2
 Build-Type:          Simple
 Cabal-Version:       >= 1.10
-extra-source-files:  README.md Changelog.md
+extra-source-files:  README.md Changelog.md include/bytestring-cpp-macros.h
 
 source-repository head
   type:     git
@@ -155,6 +155,7 @@ library
   include-dirs:      include
   includes:          fpstring.h
   install-includes:  fpstring.h
+                     bytestring-cpp-macros.h
 
 test-suite bytestring-tests
   type:             exitcode-stdio-1.0