cmake: simplify libintl check

[bkuhls]

According to https://cmake.org/cmake/help/v3.4/module/FindIntl.html
the FindIntl module already checks for libintl.so.

[bkuhls]

The previous fixes did not work out for buildroot in all cases as well, this patch fixed the remaining buildroot problem, please test on Cygwin/MacOSX & Co.

[clanmills]

@bkuhls I fixed this a couple of hours ago and tested it on Cygwin/Linux/MacOS-X.

[clanmills]

@bkuhls I've added your code INCLUDE_DIRECTORIES(${Intl_INCLUDE_DIRS}) Thank You very much for this suggestion.

[bkuhls]

With current git HEAD as of 4e86c1d the buildroot build still failed without this patch:

[100%] Linking CXX executable ../bin/exiv2
CMakeFiles/exiv2.dir/exiv2.cpp.o: In function `main':
exiv2.cpp:(.text.startup+0x1f0): undefined reference to `libintl_bindtextdomain'
exiv2.cpp:(.text.startup+0x1f8): undefined reference to `libintl_bindtextdomain'
exiv2.cpp:(.text.startup+0x200): undefined reference to `libintl_textdomain'
exiv2.cpp:(.text.startup+0x204): undefined reference to `libintl_textdomain'
libexiv2.so.26.0.0: undefined reference to `libintl_dgettext'

PS: I will try 88cf586 now and will report back.

[bkuhls]

Build is still broken with 88cf586, I will send a rebased version of this patch

[ 98%] Linking CXX executable ../bin/remotetest
libexiv2.so.26.0.0: undefined reference to `libintl_dgettext'
libexiv2.so.26.0.0: undefined reference to `libintl_bindtextdomain'
[100%] Linking CXX executable ../bin/exiv2
CMakeFiles/exiv2.dir/exiv2.cpp.o: In function `main':
exiv2.cpp:(.text.startup+0x1f0): undefined reference to `libintl_bindtextdomain'
exiv2.cpp:(.text.startup+0x1f8): undefined reference to `libintl_bindtextdomain'
exiv2.cpp:(.text.startup+0x200): undefined reference to `libintl_textdomain'
exiv2.cpp:(.text.startup+0x204): undefined reference to `libintl_textdomain'
libexiv2.so.26.0.0: undefined reference to `libintl_dgettext'

[clanmills]

I have to go out for 3 hours this morning (and later today). We'll get this fixed today. Thanks for your help.

[bkuhls]

rebased patch force-pushed to branch

[clanmills]

@bkuhls

I'm new to git and have no idea what the expression "rebased patch force-pushed to branch" means, however I've accepted your patch and it's working fine on MacOS-X/Linux/Cygwin. Very good work. Thank you very much. I'll test/fix on MSVC.