Generate INTERFACE_COMPILE_OPTIONS on export.

This was missing from commit 80ca9c4b (Add COMPILE_OPTIONS target
property., 2013-05-16).
Add compiler target compile options.

For clang, this allows passing -target <triple> to the compiler, and
for qcc, -V<arch> using toolchain files containing something like

 set(triple arm-linux-gnueabihf)
 set(CMAKE_C_COMPILER "/usr/bin/clang")
 set(CMAKE_C_COMPILER_TARGET ${triple})
 set(CMAKE_CXX_COMPILER "/usr/bin/clang++")
 set(CMAKE_CXX_COMPILER_TARGET ${triple})

or

 set(arch gcc_ntoarmv7le)
 set(CMAKE_C_COMPILER /opt/qnx650/host/linux/x86/usr/bin/qcc)
 set(CMAKE_C_COMPILER_TARGET ${arch})
 set(CMAKE_CXX_COMPILER /opt/qnx650/host/linux/x86/usr/bin/QCC)
 set(CMAKE_CXX_COMPILER_TARGET ${arch})

Both clang and qcc are inherently cross compiler( driver)s.
De-duplicate version comparison code.

Extend the VersionCompare in cmSystemTools to handle 8 components,
and port the if command to use that.
Add generator expressions for version comparision.
FindFreetype: Detect Freetype installed by GtkMM installer for win
Add missing return after error report.
Genex: Make LINK_LANGUAGE report an error when evaluating link libraries.
Genex: Extend EvaluatingLinkLibraries to also check the top target name.

This will allow testing whether we are evaluating the link libraries
of a particular target.
Genex: Report error if a target file is needed to evaluate link libraries.

Constructs such as

 target_link_libraries(foo $<$<STREQUAL:$<TARGET_FILE:foo>,foo.so>:bar>)

segfault before this patch.
Merge topic 'COMPILER_TARGET'

2d9ec1d Add compiler target compile options.
Merge topic 'export-COMPILE_OPTIONS-property'

77ff352 Generate INTERFACE_COMPILE_OPTIONS on export.
Merge topic 'version-compare-genex'

e605528 Add generator expressions for version comparision.
48bb48e De-duplicate version comparison code.
Merge topic 'FindFreetype-gtkmm'

a34839d FindFreetype: Detect Freetype installed by GtkMM installer for win
Merge topic 'dag-LINKER_LANGUAGE'

ff015ee Genex: Report error if a target file is needed to evaluate link libraries.
b58aff9 Genex: Extend EvaluatingLinkLibraries to also check the top target name.
b1c19ce Genex: Make LINK_LANGUAGE report an error when evaluating link libraries.
0e1cb07 Add missing return after error report.