Created an amalgamation without handlers, and fixed some bugs. (#283)

* Created amalgamation with upb_msg but no handlers.

* Bugfix for upb_array_resize().

* Renamed "lite" amalgamation to "core", to avoid confusion.

Traditionally "lite" has meant "without reflection", but here we
mean it as "without handlers-based code."

* Build fixes from CI tests.

* Removed some more C++-style comments.

* Fix for out-of-order statements.
diff --git a/tools/amalgamate.py b/tools/amalgamate.py
index dff1bc3..b244eff 100755
--- a/tools/amalgamate.py
+++ b/tools/amalgamate.py
@@ -11,14 +11,14 @@
   return match.groups()[0] if match else None
 
 class Amalgamator:
-  def __init__(self, output_path):
+  def __init__(self, output_path, prefix):
     self.include_paths = ["."]
     self.included = set(["upb/port_def.inc", "upb/port_undef.inc"])
-    self.output_h = open(output_path + "upb.h", "w")
-    self.output_c = open(output_path + "upb.c", "w")
+    self.output_h = open(output_path + prefix + "upb.h", "w")
+    self.output_c = open(output_path + prefix + "upb.c", "w")
 
     self.output_c.write("/* Amalgamated source file */\n")
-    self.output_c.write('#include "upb.h"\n')
+    self.output_c.write('#include "%supb.h"\n' % (prefix))
     self.output_c.write(open("upb/port_def.inc").read())
 
     self.output_h.write("/* Amalgamated source file */\n")
@@ -73,10 +73,11 @@
 # ---- main ----
 
 output_path = sys.argv[1]
-amalgamator = Amalgamator(output_path)
+prefix = sys.argv[2]
+amalgamator = Amalgamator(output_path, prefix)
 files = []
 
-for arg in sys.argv[2:]:
+for arg in sys.argv[3:]:
   arg = arg.strip()
   if arg.startswith("-I"):
     amalgamator.add_include_path(arg[2:])