Merge some detail changes.

 - [53670] Avoid C style casts.
 - [55604] Fix #3346 boost/detail/scoped_enum_emulation.hpp enum_t conflict
   with Unix rpc/types.h
 - Don't foward declare containers when using gcc's parallel library and add a
   macro to disable forward declaration. Fixes #3866.


[SVN r59679]

libs/conversion

@@ -1 +1 @@
-Subproject commit 5b6e39b2b84a8b8da7a497ed1f062d25ed52cb3f
+Subproject commit b5583b88fa88bf4d9402e35d6d2d167ff1b393f9

libs/detail

@@ -1 +1 @@
-Subproject commit 134c915cbffbb6cba961d4270f5f267713e54c50
+Subproject commit c5eac8e96c0bac9b154d5ed53bb1b0bdb590946d

libs/functional

@@ -1 +1 @@
-Subproject commit 2644aeff1236e3c744ddb96c36fb4f7f524d452e
+Subproject commit deb0e998a2e0ba63999d7ee680475c4c0d6a2d18