FindTIFF: Add imported targets and update documentation

- Add TIFF::TIFF imported target
- Document imported target
- Add testcase to test the standard variables and the imported
  target

Also:

- Add TIFF_INCLUDE_DIRS to match common practice
- Update documentation generally, including documenting
  TIFF_INCLUDE_DIRS

1 files changed, 12 insertions, 0 deletions

diff --git a/Tests/FindTIFF/Test/main.c b/Tests/FindTIFF/Test/main.c
new file mode 100644
index 0000000..fc4f337
--- /dev/null
+++ b/Tests/FindTIFF/Test/main.c
@@ -0,0 +1,12 @@
+#include <assert.h>
+#include <tiffio.h>
+
+int main()
+{
+  /* Without any TIFF file to open, test that the call fails as
+     expected.  This tests that linking worked. */
+  TIFF *tiff = TIFFOpen("invalid.tiff", "r");
+  assert(!tiff);
+
+  return 0;
+}