always use full 64 bits of address on Solaris

Solaris has somewhat nice behavior of mmaps where high bits of address
are set. It still uses only 48 bits of address on x86 (and,
presumably, 64-bit arm), just with somewhat non-standard way. But this
behavior causes some inconveniences to us. In particular, we had to
disable mmap sys allocator and had failing emergency malloc tests (due
to assertion in TryGetSizeClass in CheckCachedSizeClass). We could
consider more comprehensive fix, but lets just do "honest" 64-bit
addresses at least for now.

src/common.h

@@ -116,7 +116,7 @@ static const int kMaxDynamicFreeListLength = 8192;
 
 static const Length kMaxValidPages = (~static_cast<Length>(0)) >> kPageShift;
 
-#if __aarch64__ || __x86_64__ || _M_AMD64 || _M_ARM64
+#if (__aarch64__ || __x86_64__ || _M_AMD64 || _M_ARM64) && !__sun__
 // All current x86_64 processors only look at the lower 48 bits in
 // virtual to physical address translation. The top 16 are all same as
 // bit 47. And bit 47 value 1 reserved for kernel-space addresses in

src/system-alloc.cc

@@ -382,12 +382,6 @@ void InitSystemAllocators(void) {
   // pointer).
   DefaultSysAllocator *sdef = default_space.Construct();
   bool want_mmap = kDebugMode && (sizeof(void*) > 4);
-#if __sun__
-  // TODO: solaris has nice but annoying feature that makes it use
-  // full range of addresses and mmap tends to use it. Making mmap-ed
-  // addresses be 0xffff... For now lets avoid the trouble.
-  want_mmap = false;
-#endif
   if (want_mmap) {
     sdef->SetChildAllocator(mmap, 0, mmap_name);
     sdef->SetChildAllocator(sbrk, 1, sbrk_name);