rework header/library versioning

this replaces the changes in Issue #53 with a slightly different way of
representing / retrieving the version number.

protobuf_c_version() returns the version of the *library* as a string.

protobuf_c_version_number() returns the version of the *library* as an
integer.

PROTOBUF_C_VERSION is the version of the *headers* as a string constant.

PROTOBUF_C_VERSION_NUMBER is the version of the *headers* as an integer.

protobuf-c/libprotobuf-c.sym

@@ -4,7 +4,6 @@ global:
         protobuf_c_default_allocator;
         protobuf_c_enum_descriptor_get_value;
         protobuf_c_enum_descriptor_get_value_by_name;
-        protobuf_c_major;
         protobuf_c_message_check;
         protobuf_c_message_descriptor_get_field;
         protobuf_c_message_descriptor_get_field_by_name;
@@ -14,11 +13,12 @@ global:
         protobuf_c_message_pack;
         protobuf_c_message_pack_to_buffer;
         protobuf_c_message_unpack;
-        protobuf_c_minor;
         protobuf_c_service_descriptor_get_method_by_name;
         protobuf_c_service_destroy;
         protobuf_c_service_generated_init;
         protobuf_c_service_invoke_internal;
+        protobuf_c_version;
+        protobuf_c_version_number;
 local:
         *;
 };

protobuf-c/protobuf-c.c

@@ -84,8 +84,19 @@
 #define ASSERT_IS_SERVICE_DESCRIPTOR(desc) \
 	assert((desc)->magic == PROTOBUF_C_SERVICE_DESCRIPTOR_MAGIC)
 
-unsigned protobuf_c_major = PROTOBUF_C_MAJOR;
+/* --- version --- */
-unsigned protobuf_c_minor = PROTOBUF_C_MINOR;
+
+const char *
+protobuf_c_version(void)
+{
+	return PROTOBUF_C_VERSION;
+}
+
+uint32_t
+protobuf_c_version_number(void)
+{
+	return PROTOBUF_C_VERSION_NUMBER;
+}
 
 /* --- allocator --- */
 

protobuf-c/protobuf-c.h

@@ -58,14 +58,6 @@
 
 #define PROTOBUF_C_OFFSETOF(struct, member) offsetof(struct, member)
 
-/* The version of protobuf-c you are compiling against. */
-#define PROTOBUF_C_MAJOR	0
-#define PROTOBUF_C_MINOR	16
-
-/* The version of protobuf-c you are linking against. */
-extern unsigned protobuf_c_major;
-extern unsigned protobuf_c_minor;
-
 #if defined(_WIN32) && defined(PROTOBUF_C_USE_SHARED_LIB)
 # ifdef PROTOBUF_C_EXPORT
 #  define PROTOBUF_C_API __declspec(dllexport)
@@ -78,6 +70,39 @@ extern unsigned protobuf_c_minor;
 
 PROTOBUF_C_BEGIN_DECLS
 
+/**
+ * Get the version of the protobuf-c library. Note that this is the version of
+ * the library linked against, not the version of the headers compiled against.
+ *
+ * \return A string containing the version number of protobuf-c.
+ */
+PROTOBUF_C_API
+const char *
+protobuf_c_version(void);
+
+/**
+ * Get the version of the protobuf-c library. Note that this is the version of
+ * the library linked against, not the version of the headers compiled against.
+ *
+ * \return A 32 bit unsigned integer containing the version number of
+ *	protobuf-c, represented in base-10 as (MAJOR*1E6) + (MINOR*1E3) + PATCH.
+ */
+PROTOBUF_C_API
+uint32_t
+protobuf_c_version_number(void);
+
+/**
+ * The version of the protobuf-c headers, represented as a string using the same
+ * format as protobuf_c_version().
+ */
+#define PROTOBUF_C_VERSION		"1.0.0-pre"
+
+/**
+ * The version of the protobuf-c headers, represented as an integer using the
+ * same format as protobuf_c_version_number().
+ */
+#define PROTOBUF_C_VERSION_NUMBER	1000000
+
 typedef int protobuf_c_boolean;
 
 typedef enum {