Fix has_function() for clang on 64bit Windows
Fix has_function() for clang on 64bit Windows

has_function() tries to link an example program using the function
to see if it is available, but with clang on 64bit Windows this
example always already failed at the compile step:

error: cast from pointer to smaller type 'long' loses information
            long b = (long) a;

This is due to long!=pointer with LLP64

Change from "long" to "long long" which is min 64bit and should always
fit a pointer. While "long long" is strictly a C99 feature every
non super ancient compiler should still support it.

mesonbuild/meson,becm/meson,mesonbuild/meson,becm/meson,QuLogic/meson,QuLogic/meson,mesonbuild/meson,jpakkane/meson,mesonbuild/meson,jpakkane/meson,pexip/meson,pexip/meson,becm/meson,jpakkane/meson,QuLogic/meson,becm/meson,becm/meson,jpakkane/meson,pexip/meson,becm/meson,becm/meson,becm/meson,pexip/meson,pexip/meson,QuLogic/meson,pexip/meson,pexip/meson,pexip/meson,pexip/meson,mesonbuild/meson,QuLogic/meson,mesonbuild/meson,jpakkane/meson,pexip/meson,jpakkane/meson,becm/meson,QuLogic/meson,QuLogic/meson,mesonbuild/meson,mesonbuild/meson,jpakkane/meson,mesonbuild/meson,QuLogic/meson,jpakkane/meson,QuLogic/meson,becm/meson,mesonbuild/meson,jpakkane/meson