Add more version-related defines (#1131)

Add NOTCURSES_VERNUM_* as integer preprocessor definitions of
the four version components. Add NOTCURSES_VERNUM_ORDERED as
a 32-bit totally comparable integer. Preserve the definitions
of NOTCURSES_VERSION_*, defining them in terms of VERNUMs.
Don't use TWEAK in version, since it usually isn't defined.

tools/version.h.in

@@ -2,6 +2,16 @@
 #ifndef NOTCURSES_VERSION_HEADER
 #define NOTCURSES_VERSION_HEADER
 
+#define NOTCURSES_VERNUM_MAJOR @notcurses_VERSION_MAJOR@
+#define NOTCURSES_VERNUM_MINOR @notcurses_VERSION_MINOR@
+#define NOTCURSES_VERNUM_PATCH @notcurses_VERSION_PATCH@
+#define NOTCURSES_VERNUM_TWEAK @notcurses_VERSION_TWEAK@
+
+#define NOTCURSES_VERNUM_ORDERED \
+ ((NOTCURSES_VERNUM_MAJOR << 16u) + \
+  (NOTCURSES_VERNUM_MINOR << 8u) + \
+  (NOTCURSES_VERNUM_PATCH))
+
 #define NOTCURSES_VERSION_MAJOR "@notcurses_VERSION_MAJOR@"
 #define NOTCURSES_VERSION_MINOR "@notcurses_VERSION_MINOR@"
 #define NOTCURSES_VERSION_PATCH "@notcurses_VERSION_PATCH@"