8169373: Work around linux NPTL stack guard error.
Summary: Also skip libc guard page for compiler thread, merge similar code on linux platforms, and streamline libc guard page handling on linuxs390, linuxppc, aixppc.
Reviewed-by: dholmes, dcubed, kvn

8140520: segfault on solaris-amd64 with "-XX:VMThreadStackSize=1" option
Summary: Split the single thread_min_stack_allowed into three distinct values (java_thread_min_stack_allowed, compiler_thread_min_stack_allowed and vm_internal_thread_min_stack_allowed) on non-Windows platforms.
Reviewed-by: dcubed, gthornbr, dholmes, coleenp, fparain, aph

8159335: Fix problems with stack overflow handling.
Reviewed-by: dlong, coleenp, mdoerr

8156923: [ppc] Implement "JEP 270: Reserved Stack Areas for Critical Sections".
Reviewed-by: simonis, dholmes

8147937: Adapt SAP copyrights to new company name.
Reviewed-by: simonis, stuefe

8145114: const-correctness for ucontext_t* reading functions
Reviewed-by: dholmes, coleenp

8144847: PPC64: Update Transactional Memory and Atomic::cmpxchg code
Reviewed-by: stuefe, goetz

8143125: [aix] Further Developments for AIX
Summary: Port newest AIX port developemnts to OpenJDK.
Reviewed-by: goetz, simonis

8141529: Fix handling of _JAVA_SR_SIGNUM
Reviewed-by: dholmes, stuefe, dsamersoff

8080298: Clean up os::...::supports_variable_stack_size()
Reviewed-by: kbarrett, simonis, stuefe, coleenp

8075505: aix: improve handling of native memory
Reviewed-by: kvn, stuefe
Contributed-by: thomas.stuefe@sap.com

8066964: ppc64: argument and return type profiling, fix problem with popframe
Reviewed-by: roland, kvn

8023038: PPC64 (part 15): Platform files for AIX/PPC64 support
Reviewed-by: kvn