Reland "[WebAssembly] Add support for naming wasm data segments"

Add adds support for naming data segments.  This is useful
useful linkers so that they can merge similar sections.

Differential Revision: https://reviews.llvm.org/D37886

llvm-svn: 313795
diff --git a/llvm/test/MC/WebAssembly/array-fill.ll b/llvm/test/MC/WebAssembly/array-fill.ll
index 4feabc0..38274c3 100644
--- a/llvm/test/MC/WebAssembly/array-fill.ll
+++ b/llvm/test/MC/WebAssembly/array-fill.ll
@@ -9,6 +9,14 @@
 
 @gBd = hidden global [2 x %struct.bd] [%struct.bd { i8 1 }, %struct.bd { i8 2 }], align 1
 
-; CHECK:  - Type:            DATA
-; CHECK:        Content:         '0102'
-; CHECK:    DataSize:        2
+; CHECK:        - Type:            DATA
+; CHECK:              Content:         '0102'
+
+; CHECK:        - Type:            CUSTOM
+; CHECK-NEXT:     Name:            linking
+; CHECK-NEXT:     DataSize:        2
+; CHECK-NEXT:     DataAlignment:   1
+; CHECK-NEXT:     SegmentNames:    
+; CHECK-NEXT:       - Index:           0
+; CHECK-NEXT:         Name:            .data
+; CHECK-NEXT: ...