genmidi: Import remaining horncomposer changes.

This adds the remaining changes from horncomposer's modified version
of the old GENMIDI lump. Details from his accompanying text file
follow:

2/6/11- Replaced Electric Piano 2 (patch 5) - with the high pitched attack :)
        Replaced Acoustic Piano (patch 0) - Serves as model for other pianos
        Replaced Bright Acoustic Piano (patch 1)
        Replaced Electric Grand Piano (patch 2)
        Replaced Honky-tonk piano (patch 3) - Added "out of tune"
        Accidentally discovered a good Electic Piano 1 (patch 4) - with chorus

lumps/genmidi/config.py

@@ -71,8 +71,10 @@ INSTRUMENTS = [
 	Instrument("instr001.sbi"),             # #001 - Acoustic Grand Piano
 	Instrument("instr002.sbi"),             # #002 - Bright Acoustic Piano
 	Instrument("instr003.sbi"),             # #003 - Electric Grand Piano
-	Instrument("instr004.sbi"),             # #004 - Honky-tonk Piano
-	Instrument("instr005.sbi"),             # #005 - Electric Piano 1
+	Instrument("instr004.sbi",              # #004 - Honky-tonk Piano
+	           "instr004-2.sbi"),
+	Instrument("instr005.sbi",              # #005 - Electric Piano 1
+	           "instr005-2.sbi"),
 	Instrument("instr006.sbi"),             # #006 - Electric Piano 2
 	Instrument("instr007.sbi"),             # #007 - Harpsichord
 	Instrument("instr008.sbi"),             # #008 - Clavi