Add custom assertion mechanism with backtrace printing

[Praetonus]

This change will allow getting more complete reports from assertion failures. This will smooth the the bug report process, as users won't have to get a backtrace from a debugger. As part of this change, assertions are now enabled in release builds of the compiler, as discussed in #1553. They still are disabled in release builds of the runtime.

In the future, this system could be extended with even more precise information like line numbers. Parsing the debug information of the executables and libraries will be required for this.

Closes #1553.

PS: The tests should all fail, I've added an always firing assertion to check if the backtrace report works correctly on all systems.

[Praetonus]

The tests are failing correctly. I'll update the PR to remove the assertion.

[sylvanc]

Very odd: debug build on Windows is failing to find some symbols at link time.

[chalcolith]

The stack trace functions are in an additional library:

diff --git a/src/libponyc/platform/vcvars.c b/src/libponyc/platform/vcvars.c
index 266f270..f9c810a 100644
--- a/src/libponyc/platform/vcvars.c
+++ b/src/libponyc/platform/vcvars.c
@@ -173,7 +173,7 @@ static bool find_kernel32(vcvars_t* vcvars, errors_t* errors)
   vcvars->ucrt[0] = '\0';
   strcpy(vcvars->default_libs,
     "kernel32.lib msvcrt.lib Ws2_32.lib advapi32.lib "
-    "vcruntime.lib legacy_stdio_definitions.lib");
+    "vcruntime.lib legacy_stdio_definitions.lib dbghelp.lib");

   strcpy(vcvars->kernel32, sdk.path);
   strcat(vcvars->kernel32, "Lib\\");

[Praetonus]

Thanks @kulibali. I've updated the PR.

[Praetonus]

Conflicts resolved.

[Praetonus]

And errors fixed.

[jemc]

I'm still compiling with clang version 3.5.0 on Linux x64, and this seems to break the build for me.

In file included from src/libponyc/codegen/gendebug.cc:15:
In file included from /home/jemc/1/code/tarx/llvm-3.9.0.src.rel/build/install/include/llvm/IR/DIBuilder.h:18:
In file included from /home/jemc/1/code/tarx/llvm-3.9.0.src.rel/build/install/include/llvm/IR/DebugInfo.h:21:
In file included from /home/jemc/1/code/tarx/llvm-3.9.0.src.rel/build/install/include/llvm/ADT/SmallVector.h:29:
In file included from /usr/bin/../lib/gcc/x86_64-redhat-linux/5.3.1/../../../../include/c++/5.3.1/memory:83:
In file included from /usr/bin/../lib/gcc/x86_64-redhat-linux/5.3.1/../../../../include/c++/5.3.1/bits/shared_ptr_atomic.h:33:
/usr/bin/../lib/gcc/x86_64-redhat-linux/5.3.1/../../../../include/c++/5.3.1/bits/atomic_base.h:160:3: error: 
      declaration of anonymous struct must be a definition
  struct atomic_flag : public __atomic_flag_base
  ^
In file included from src/libponyc/codegen/gendebug.cc:15:
In file included from /home/jemc/1/code/tarx/llvm-3.9.0.src.rel/build/install/include/llvm/IR/DIBuilder.h:18:
In file included from /home/jemc/1/code/tarx/llvm-3.9.0.src.rel/build/install/include/llvm/IR/DebugInfo.h:23:
In file included from /home/jemc/1/code/tarx/llvm-3.9.0.src.rel/build/install/include/llvm/IR/DebugInfoMetadata.h:17:
In file included from /home/jemc/1/code/tarx/llvm-3.9.0.src.rel/build/install/include/llvm/IR/Metadata.h:26:
In file included from /home/jemc/1/code/tarx/llvm-3.9.0.src.rel/build/install/include/llvm/IR/LLVMContext.h:19:
In file included from /home/jemc/1/code/tarx/llvm-3.9.0.src.rel/build/install/include/llvm/Support/Options.h:41:
In file included from /home/jemc/1/code/tarx/llvm-3.9.0.src.rel/build/install/include/llvm/Support/CommandLine.h:29:
In file included from /home/jemc/1/code/tarx/llvm-3.9.0.src.rel/build/install/include/llvm/Support/ManagedStatic.h:18:
/usr/bin/../lib/gcc/x86_64-redhat-linux/5.3.1/../../../../include/c++/5.3.1/atomic:894:15: error: member reference
      base type 'bool' is not a structure or union
  { return __a->test_and_set(__m); }
           ~~~^ ~~~~~~~~~~~~
/usr/bin/../lib/gcc/x86_64-redhat-linux/5.3.1/../../../../include/c++/5.3.1/atomic:899:15: error: member reference
      base type 'volatile bool' is not a structure or union
  { return __a->test_and_set(__m); }
           ~~~^ ~~~~~~~~~~~~
/usr/bin/../lib/gcc/x86_64-redhat-linux/5.3.1/../../../../include/c++/5.3.1/atomic:903:8: error: member reference
      base type 'bool' is not a structure or union
  { __a->clear(__m); }
    ~~~^ ~~~~~
/usr/bin/../lib/gcc/x86_64-redhat-linux/5.3.1/../../../../include/c++/5.3.1/atomic:908:8: error: member reference
      base type 'volatile bool' is not a structure or union
  { __a->clear(__m); }
    ~~~^ ~~~~~
5 errors generated.
Makefile:654: recipe for target 'build/debug/obj/libponyc/codegen/gendebug.o' failed
make: *** [build/debug/obj/libponyc/codegen/gendebug.o] Error 1

[Praetonus]

I guess putting a define on atomic_flag wasn't a good idea. I'll make a fix right away.