Fix testsuite regression by: Do not skip prologue for asm (.S) files

I have somehow missed gdb.asm/asm-source.exp PASS->FAIL even on x86_64.

It has no longer valid assumption that "break" breaks after the prologue even
in assembler.  So I have changed this assumption of the testfile.

gdb/testsuite/ChangeLog
2015-07-10  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb.asm/asm-source.exp (f at main): Stop at gdbasm_enter.
	(n at main): New.
	* gdb.asm/asmsrc1.s: Add comment "mark: main enter".

gdb/testsuite/ChangeLog

@@ -1,3 +1,9 @@
+2015-07-10  Jan Kratochvil  <jan.kratochvil@redhat.com>
+
+	* gdb.asm/asm-source.exp (f at main): Stop at gdbasm_enter.
+	(n at main): New.
+	* gdb.asm/asmsrc1.s: Add comment "mark: main enter".
+
 2015-07-10  Andreas Arnez  <arnez@linux.vnet.ibm.com>
 
 	* gdb.base/gnu_vector.exp: On x86 and x86_64 targets, skip the

gdb/testsuite/gdb.asm/asm-source.exp

@@ -275,6 +275,7 @@ if { [istarget "m6811-*-*"] || [istarget "m6812-*-*"] } {
 }
 
 # Collect some line numbers.
+set line_enter      [expr [gdb_get_line_number "main enter" "asmsrc1.s"] + 1]
 set line_main       [expr [gdb_get_line_number "main start" "asmsrc1.s"] + 1]
 set line_call_foo2  [expr [gdb_get_line_number "call foo2"  "asmsrc1.s"] + 1]
 set line_search_comment [expr [gdb_get_line_number "search" "asmsrc1.s"] + 1]
@@ -298,7 +299,10 @@ if ![runto_main] then {
 }
 
 # Execute the `f' command and see if the result includes source info.
-gdb_test "f" "asmsrc1\[.\]s:$line_main.*several_nops" "f at main"
+gdb_test "f" "asmsrc1\[.\]s:$line_enter.*gdbasm_enter" "f at main"
+
+# Execute the `n' command.
+gdb_test "n" "$line_main\[ 	\]*.*several_nops" "n at main"
 
 # See if we properly `next' over a macro with several insns.
 gdb_test "n" "$line_call_foo2\[ 	\]*.*foo2" "next over macro"

gdb/testsuite/gdb.asm/asmsrc1.s

@@ -34,6 +34,7 @@
 
 	.global main
 	gdbasm_declare main
+	comment "mark: main enter"
 	gdbasm_enter
 
 	comment "Call a macro that consists of several lines of assembler code."