Improve version information

Add version number and string as macros and symbols. Version numbers can
be easily compared, for example in the C preprocessor:

    #include <cmark.h>

    #if CMARK_VERSION < 0x020200
    #error Requires libcmark 2.2.0 or higher
    #endif

Storing the version in a global variable allows to check the library
version at runtime. For example:

    if (CMARK_VERSION != cmark_version) {
        warn("Compiled against libcmark %s, but using %s",
             CMARK_VERSION_STRING, cmark_version_string);
    }

The version should be updated whenever the public API is changed.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/main.c b/src/main.c
index 5855868..ef40a88 100644
--- a/src/main.c
+++ b/src/main.c
@@ -73,7 +73,7 @@ int main(int argc, char *argv[])
 
 	for (i = 1; i < argc; i++) {
 		if (strcmp(argv[i], "--version") == 0) {
-			printf("cmark %s", CMARK_VERSION);
+			printf("cmark %s", CMARK_VERSION_STRING);
 			printf(" - CommonMark converter (c) 2014 John MacFarlane\n");
 			exit(0);
 		} else if (strcmp(argv[i], "--sourcepos") == 0) {