re2: update to 2020-04-01

Massive cleanup of Makefile.

Remove inactive maintainer.

Remove completely unused host build.

Shorten title so that it shows under menuconfig.

Remove pointless static/shared choice.

Add C++17 patch as libcxx seems to need it with this package.

Add ABI_VERSION.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

libs/libre2/patches/010-cxx17.patch

@@ -0,0 +1,23 @@
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -38,9 +38,9 @@ if(CMAKE_CXX_COMPILER_ID MATCHES "MSVC")
+   add_compile_options(/utf-8)
+ elseif(CYGWIN OR MINGW)
+   # See https://stackoverflow.com/questions/38139631 for details.
+-  add_compile_options(-std=gnu++11)
++  add_compile_options(-std=gnu++17)
+ elseif(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
+-  add_compile_options(-std=c++11)
++  add_compile_options(-std=c++17)
+ endif()
+ 
+ if(WIN32)
+--- a/re2.pc
++++ b/re2.pc
+@@ -6,5 +6,5 @@ libdir=@libdir@
+ Name: re2
+ Description: RE2 is a fast, safe, thread-friendly regular expression engine.
+ Version: 0.0.0
+-Cflags: -std=c++11 -pthread -I${includedir}
++Cflags: -std=c++17 -pthread -I${includedir}
+ Libs: -pthread -L${libdir} -lre2