patch 9.0.0007: no support for double, dotted and dashed underlines

Problem:    No support for double, dotted and dashed underlines.
Solution:   Add the termcap entries and highlight modes. (closes #9553)
diff --git a/src/term.c b/src/term.c
index b365831..754ef82 100644
--- a/src/term.c
+++ b/src/term.c
@@ -1187,6 +1187,9 @@
     {(int)KS_US,	"[US]"},
     {(int)KS_UCE,	"[UCE]"},
     {(int)KS_UCS,	"[UCS]"},
+    {(int)KS_USS,	"[USS]"},
+    {(int)KS_DS,	"[DS]"},
+    {(int)KS_CDS,	"[CDS]"},
     {(int)KS_STE,	"[STE]"},
     {(int)KS_STS,	"[STS]"},
     {(int)KS_MS,	"[MS]"},
@@ -1669,6 +1672,7 @@
 			{KS_MD, "md"}, {KS_SE, "se"}, {KS_SO, "so"},
 			{KS_CZH,"ZH"}, {KS_CZR,"ZR"}, {KS_UE, "ue"},
 			{KS_US, "us"}, {KS_UCE, "Ce"}, {KS_UCS, "Cs"},
+			{KS_USS, "Us"}, {KS_DS, "ds"}, {KS_CDS, "Ds"},
 			{KS_STE,"Te"}, {KS_STS,"Ts"},
 			{KS_CM, "cm"}, {KS_SR, "sr"},
 			{KS_CRI,"RI"}, {KS_VB, "vb"}, {KS_KS, "ks"},