Config: Fix up cygwin support as follows:

* Define BOOST_HAS_STDINT_H in more situations.
* Disable BOOST_NO_CXX14_HDR_SHARED_MUTEX in -std=c++XX mode as the std header doesn't compile (cygwin bug).
* Add more tests to CI.

appveyor.yml

@@ -30,14 +30,18 @@ environment:
     - ARGS: --toolset=msvc-12.0 address-model=64
     - ARGS: --toolset=msvc-14.0 address-model=64
     - ARGS: --toolset=msvc-14.0 address-model=64 cxxflags=-std:c++latest
-    - ARGS: --toolset=gcc address-model=64
+    - ARGS: --toolset=gcc address-model=64 cxxstd=03,11,14,1z
       PATH: C:\mingw-w64\x86_64-6.3.0-posix-seh-rt_v5-rev1\mingw64\bin;%PATH%
-    - ARGS: --toolset=gcc address-model=64 cxxflags=-std=gnu++1z
-      PATH: C:\mingw-w64\x86_64-6.3.0-posix-seh-rt_v5-rev1\mingw64\bin;%PATH%
-    - ARGS: --toolset=gcc address-model=32
-      PATH: C:\mingw-w64\i686-5.3.0-posix-dwarf-rt_v4-rev0\mingw32\bin;%PATH%
-    - ARGS: --toolset=gcc address-model=32 linkflags=-Wl,-allow-multiple-definition
+    - ARGS: --toolset=gcc address-model=64 cxxstd=03,11,14,1z
+      PATH: C:\mingw-w64\i686-5.3.0-posix-dwarf-rt_v4-rev0\mingw64\bin;%PATH%
+    - ARGS: --toolset=gcc address-model=64 cxxstd=03,11,14,1z
+      PATH: C:\mingw-w64\x86_64-7.2.0-posix-seh-rt_v5-rev1\mingw64\bin;%PATH%
+    - ARGS: --toolset=gcc address-model=32 linkflags=-Wl,-allow-multiple-definition cxxstd=03,11,14,1z
       PATH: C:\MinGW\bin;%PATH%
+    - ARGS: --toolset=gcc address-model=64 cxxstd=03,11,14,1z
+      PATH: C:\cygwin64\bin;%PATH%
+    - ARGS: --toolset=gcc address-model=32 cxxstd=03,11,14,1z
+      PATH: C:\cygwin\bin;%PATH%
 
 install:
   - cd ..

include/boost/config/platform/cygwin.hpp

@@ -38,10 +38,21 @@
 #ifdef _STDINT_H
 #define BOOST_HAS_STDINT_H
 #endif
+#if __GNUC__ > 5 && !defined(BOOST_HAS_STDINT_H)
+#   define BOOST_HAS_STDINT_H
+#endif
 
 /// Cygwin has no fenv.h
 #define BOOST_NO_FENV_H
 
+// Cygwin has it's own <pthread.h> which breaks <shared_mutex> unless the correct compiler flags are used:
+#ifndef BOOST_NO_CXX14_HDR_SHARED_MUTEX
+#include <pthread.h>
+#if !(__XSI_VISIBLE >= 500 || __POSIX_VISIBLE >= 200112)
+#  define BOOST_NO_CXX14_HDR_SHARED_MUTEX
+#endif
+#endif
+
 // boilerplate code:
 #include <boost/config/detail/posix_features.hpp>
 

include/boost/cstdint.hpp

@@ -60,7 +60,7 @@
 #   include <stdint.h>
 
 // There is a bug in Cygwin two _C macros
-#   if defined(__STDC_CONSTANT_MACROS) && defined(__CYGWIN__)
+#   if defined(INTMAX_C) && defined(__CYGWIN__)
 #     undef INTMAX_C
 #     undef UINTMAX_C
 #     define INTMAX_C(c) c##LL