package/boost: cleanup boost-context/fiber/math

boost-context
- requires C++11 (gcc 4.8) since 1.61 see [0]
- dropped the dependency on (boost) thread in 1.77 see [1]
boost-fiber
- needed C++11 since it's creation in 1.61 [2]
boost-math
- add comment for gcc version

[0] https://www.boost.org/doc/libs/1_82_0/libs/context/doc/html/context/requirements.html
[1] https://github.com/boostorg/context/commit/8425e830eab0ad550db937027392c4b4a54df695
[2] https://www.boost.org/doc/libs/1_62_0/libs/fiber/doc/html/fiber/overview.html

Signed-off-by: Michael Nosthoff <buildroot@heine.tech>
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>

package/boost/Config.in

@@ -50,13 +50,14 @@ config BR2_PACKAGE_BOOST_CONTEXT_ARCH_SUPPORTS
 config BR2_PACKAGE_BOOST_CONTEXT
 	bool "boost-context"
 	depends on BR2_PACKAGE_BOOST_CONTEXT_ARCH_SUPPORTS
-	depends on BR2_TOOLCHAIN_SUPPORTS_ALWAYS_LOCKFREE_ATOMIC_INTS \
-		|| BR2_TOOLCHAIN_GCC_AT_LEAST_6 # boost-thread
+	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_4_8
 	depends on !BR2_TOOLCHAIN_HAS_GCC_BUG_64735
-	select BR2_PACKAGE_BOOST_THREAD if !BR2_TOOLCHAIN_GCC_AT_LEAST_6
 	help
 	  C++11 context switching library.
 
+comment "boost-context needs a toolchain w/ C++11, gcc>=4.8"
+	depends on !BR2_TOOLCHAIN_GCC_AT_LEAST_4_8
+
 config BR2_PACKAGE_BOOST_CONTRACT
 	bool "boost-contract"
 	# pthread_condattr_setclock
@@ -72,16 +73,20 @@ config BR2_PACKAGE_BOOST_COROUTINE
 	bool "boost-coroutine"
 	depends on BR2_PACKAGE_BOOST_CONTEXT_ARCH_SUPPORTS
 	depends on BR2_TOOLCHAIN_SUPPORTS_ALWAYS_LOCKFREE_ATOMIC_INTS # boost-thread
+	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_4_8 # boost-context
 	depends on !BR2_TOOLCHAIN_HAS_GCC_BUG_64735 # boost-context, boost-thread
 	select BR2_PACKAGE_BOOST_CHRONO
 	select BR2_PACKAGE_BOOST_CONTEXT
 	select BR2_PACKAGE_BOOST_SYSTEM
 	select BR2_PACKAGE_BOOST_THREAD
 	help
-	  deprecated coroutine library, the non-depricated coroutine2
+	  deprecated coroutine library, the non-deprecated coroutine2
 	  library is a header-only library and does not need to be
 	  selected.
 
+comment "boost-coroutine needs a toolchain w/ C++11, gcc>=4.8"
+	depends on !BR2_TOOLCHAIN_GCC_AT_LEAST_4_8
+
 comment "boost-coroutine needs a toolchain not affected by GCC bug 64735"
 	depends on BR2_PACKAGE_BOOST_CONTEXT_ARCH_SUPPORTS
 	depends on BR2_TOOLCHAIN_SUPPORTS_ALWAYS_LOCKFREE_ATOMIC_INTS
@@ -109,21 +114,20 @@ config BR2_PACKAGE_BOOST_FIBER
 	depends on !BR2_MIPS_CPU_MIPS32 && !BR2_MIPS_CPU_MIPS64
 	depends on BR2_TOOLCHAIN_SUPPORTS_ALWAYS_LOCKFREE_ATOMIC_INTS # boost-filesystem
 	depends on !BR2_TOOLCHAIN_HAS_GCC_BUG_64735 # boost-context
+	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_4_8
 	select BR2_PACKAGE_BOOST_CONTEXT
 	select BR2_PACKAGE_BOOST_FILESYSTEM
 	select BR2_PACKAGE_BOOST_SYSTEM
 	help
 	  C++11 userland threads library.
 
-comment "boost-fiber needs a toolchain w/ NPTL"
+comment "boost-fiber needs a toolchain w/ NPTL, C++11, gcc>=4.8"
 	depends on BR2_PACKAGE_BOOST_CONTEXT_ARCH_SUPPORTS
-	depends on BR2_TOOLCHAIN_SUPPORTS_ALWAYS_LOCKFREE_ATOMIC_INTS
-	depends on !BR2_TOOLCHAIN_HAS_THREADS_NPTL
+	depends on !BR2_TOOLCHAIN_HAS_THREADS_NPTL \
+		|| !BR2_TOOLCHAIN_GCC_AT_LEAST_4_8
 
 comment "boost-fiber needs a toolchain not affected by GCC bug 64735"
 	depends on BR2_PACKAGE_BOOST_CONTEXT_ARCH_SUPPORTS
-	depends on BR2_TOOLCHAIN_SUPPORTS_ALWAYS_LOCKFREE_ATOMIC_INTS \
-		|| BR2_TOOLCHAIN_GCC_AT_LEAST_6
 	depends on BR2_TOOLCHAIN_HAS_GCC_BUG_64735
 
 config BR2_PACKAGE_BOOST_FILESYSTEM
@@ -242,6 +246,9 @@ config BR2_PACKAGE_BOOST_MATH
 	  Octonions, like quaternions, are a relative of complex
 	  numbers.
 
+comment "boost-math needs a toolchain w/ C++14, gcc>=5.0"
+	depends on !BR2_TOOLCHAIN_GCC_AT_LEAST_5
+
 config BR2_PACKAGE_BOOST_MPI
 	bool "boost-mpi"
 	help