Added check for stdbool.h header and forcing its use (#159)

When compiling YARA without Python bindings, stdbool.h is actually used
if it can be used. However Python bindings completely ignore it resulting
in YARA defining its own bool type with sizeof(bool) == sizeof(int).
However before [#1377](https://github.com/VirusTotal/yara/pull/1377), this
can result in different compilation units using different sizes of
bool type and chaos ensues.

setup.py

@@ -87,6 +87,23 @@ def has_function(function_name, libraries=None):
   return result
 
 
+def has_header(header_name):
+  compiler = distutils.ccompiler.new_compiler()
+  with muted(sys.stdout, sys.stderr):
+    with tempfile.NamedTemporaryFile(mode='w', prefix=header_name, delete=False, suffix='.c') as f:
+      f.write("""
+#include <{}>
+
+int main() {{ return 0; }}
+      """.format(header_name))
+      f.close()
+      try:
+        compiler.compile([f.name])
+      except distutils.errors.CompileError:
+        return False
+  return True
+
+
 class BuildCommand(build):
 
   user_options = build.user_options + OPTIONS
@@ -221,6 +238,9 @@ class BuildExtCommand(build_ext):
       module.define_macros.append(('USE_NO_PROC', '1'))
       module.extra_compile_args.append('-std=c99')
 
+    if has_header('stdbool.h'):
+      module.define_macros.append(('HAVE_STDBOOL_H', '1'))
+
     if has_function('memmem'):
       module.define_macros.append(('HAVE_MEMMEM', '1'))
     if has_function('strlcpy'):