Document our supported rpmdb indexes in the API via an enum of their own

- Now that our indexes are actually hardwired in the code we can
  properly separate rpmtag vs db index names.
- Defined similarly to rpmTags, with rpmDbiTag being the "true enum"
  and rpmDbiTagVal the integral type they present. As many of the
  indexes are defined via RPMTAG values (and need to remain that
  way to avoid breaking every single API user) we need to have a
  compatible type with rpmTags.
- These would logically belong to rpmdb.h but keeping in rpmtag.h
  to have them available "everywhere", we can't go including rpmdb.h
  from rpmtag.h so keeping them here avoids potential unnecessary breakage.

lib/rpmtag.h

@@ -7,12 +7,6 @@
 extern "C" {
 #endif
 
-/**
- * Pseudo-tags used by the rpmdb and rpmgi iterator API's.
- */
-#define	RPMDBI_PACKAGES		0	/* Installed package headers. */
-#define	RPMDBI_LABEL		2	/* Fingerprint search marker. */
-
 /**
  * Header private tags.
  * @note General use tags should start at 1000 (RPM's tag space starts there).
@@ -309,6 +303,26 @@ typedef enum rpmTag_e {
 
 #define	RPMTAG_EXTERNAL_TAG		1000000
 
+/** \ingroup rpmtag
+ * Rpm database index tags.
+ */
+typedef enum rpmDbiTag_e {
+    RPMDBI_PACKAGES		= 0,	/* Installed package headers. */
+    RPMDBI_LABEL		= 2,	/* NEVRA label pseudo index */
+    RPMDBI_NAME			= RPMTAG_NAME,
+    RPMDBI_BASENAMES		= RPMTAG_BASENAMES,
+    RPMDBI_GROUP		= RPMTAG_GROUP,
+    RPMDBI_REQUIRENAME		= RPMTAG_REQUIRENAME,
+    RPMDBI_PROVIDENAME		= RPMTAG_PROVIDENAME,
+    RPMDBI_CONFLICTNAME		= RPMTAG_CONFLICTNAME,
+    RPMDBI_OBSOLETENAME		= RPMTAG_OBSOLETENAME,
+    RPMDBI_TRIGGERNAME		= RPMTAG_TRIGGERNAME,
+    RPMDBI_DIRNAMES		= RPMTAG_DIRNAMES,
+    RPMDBI_INSTALLTID		= RPMTAG_INSTALLTID,
+    RPMDBI_SIGMD5		= RPMTAG_SIGMD5,
+    RPMDBI_SHA1HEADER		= RPMTAG_SHA1HEADER,
+} rpmDbiTag;
+
 /** \ingroup signature
  * Tags found in signature header from package.
  */

lib/rpmtypes.h

@@ -28,6 +28,7 @@ typedef int32_t		rpm_tag_t;
 typedef uint32_t	rpm_tagtype_t;
 typedef uint32_t	rpm_count_t;
 typedef rpm_tag_t	rpmTagVal;
+typedef rpm_tag_t	rpmDbiTagVal;
 
 typedef void *		rpm_data_t;
 typedef const void *	rpm_constdata_t;