Boost: patch for context/coroutine libraries for LoP PPC64

[Tony Reix]

Hello

I'm preparing a patch for Boost v1.55 for context & coroutine libraries for Linux on Power PPC64 LITTLE Endian.
The code is the same (using #if) for Boost v1.55 for context & coroutine libraries for Linux on Power PPC64 BIG Endian.

Files :
libs/context/src/asm/jump_ppc64_sysv_elf_gas.S
libs/context/src/asm/make_ppc64_sysv_elf_gas.S

The current files of Boost v1.55 delivered by Ubuntu 14.04 for Linux on Power PPC64 LE (& BE) generate a segfault for the tests of the 2 libraries context & coroutine.

The current code of context & coroutine libraries in "develop" version of Boost has changed. API has changed. Thus, the patches for Boost v1.55 and for future version of Boost will be different. I'll deliver them in parallel (for Ubuntu and for Boost project).

I have built files that make the Boost v1.55 context and coroutine tests work fine on Linux on Power PPC64 LE & BE.
However, I have no way to test on other different PPC environment.

The lines that control compiling these .S files are (in file libs/context/build/Jamfile.v2) :

# POWERPC_64
alias asm_context_sources
   : asm/make_ppc64_sysv_elf_gas.S
     asm/jump_ppc64_sysv_elf_gas.S
   : <address-model>64
     <architecture>power
     <binary-format>elf
     <toolset>gcc
   ;

I do not master Jam, and I don't know if these lines are used by other PPC64 environment.
So, if you use my changes for modifying the Boost source code used by Ubuntu 14.04 only for IBM PowerPC64 machines with Linux BE or LE, that will work fine.
If the way you manage source code is centralized for different targets (including other PPC64 environments I'm not aware of), that should not work, and files should be named in a different way, and the Jamfile.v2 will have to be changed too .

I need some advice.

Regards,
Tony