cmd/5l, cmd/6l, cmd/8l: fix function symbol generation from gcc compiled source code

For CL 6853059.

R=jsing, rsc
CC=golang-dev
https://golang.org/cl/6938076

src/cmd/5l/asm.c

@@ -450,7 +450,7 @@ adddynsym(Sym *s)
 
 		/* type */
 		t = STB_GLOBAL << 4;
-		if(s->dynexport && s->type == STEXT)
+		if(s->dynexport && (s->type&SMASK) == STEXT)
 			t |= STT_FUNC;
 		else
 			t |= STT_OBJECT;

src/cmd/6l/asm.c

@@ -455,7 +455,7 @@ adddynsym(Sym *s)
 		adduint32(d, addstring(lookup(".dynstr", 0), name));
 		/* type */
 		t = STB_GLOBAL << 4;
-		if(s->dynexport && s->type == STEXT)
+		if(s->dynexport && (s->type&SMASK) == STEXT)
 			t |= STT_FUNC;
 		else
 			t |= STT_OBJECT;

src/cmd/8l/asm.c

@@ -447,7 +447,7 @@ adddynsym(Sym *s)
 	
 		/* type */
 		t = STB_GLOBAL << 4;
-		if(s->dynexport && s->type == STEXT)
+		if(s->dynexport && (s->type&SMASK) == STEXT)
 			t |= STT_FUNC;
 		else
 			t |= STT_OBJECT;