* Added readme.

* Fixed bugs

* some small improvements and bug fixes

handle header without extension

handle objeclib only input for target

if compiler num is 0 this is not always an error,
as that  can also happen, when having only a objectlib
as input and no other source files.

Fix unclear error while accidentally sanitizing interface library

Interface libraries added since CMake 3.0 version have INTERFACE_SOURCES property instead of SOURCES so it leads to error which is unclear and prevents project from compiling. Warning would be enough it this case.

Fix language detection with file names containing more than one dot

Fix reference to sanitizer_add_blacklist_file in README.md

Reenable TSan on macOS as newer Xcode toolchains support it.

Fix a couple of spelling typos

Fix option type in add_sanitizers check

Show fewer warnings for targets.

Instead of printing the same message over and over again, if a target can't use
a specific sanitizer, the message will be printed only once for the first
affected target now.

Fixed links.

Fixed links in README.md after merge to upstream.

Restructuring and new features

In some special cases static linking the sanitizers won't work, and you have to
preload libasan. To find the right libasan depending on the application to be
executed, a wrapper script was added. The location of the wrapper script can be
accessed via ASan_WRAPPER variable.

If you like to preload a sanitized library in front of an application, it will
fail, because it is not the first in the library list anymore. This behaviour
is gcc specific - clang will static link the sanitizers instead. To get the
same for gcc, the new SANITIZE_LINK_STATIC flag will link the sanitizers
static in gcc environments.

Note: The preloaded executable must be sanitized, too! Otherwise ASan will
      print an error message!

Due optimizing the code is optional for using the sanitizers, the user should
set an optimisation level by his choice on his own.

Some sanitizers are not compatible with other sanitizers. Added some checks to
avoid these combinations at configuration time.