gdb.base/sym-file.exp: clean up test messages a bit.

Remove regex characters from test message, and don't refer to
breakpoint numbers in test messages (subsequent patches will add more
breakpoints, changing these numbers).  Result:

 -PASS: gdb.base/sym-file.exp: add-symbol-file .*sym-file-lib\.so addr
 +PASS: gdb.base/sym-file.exp: add-symbol-file sym-file-lib.so addr

 -PASS: gdb.base/sym-file.exp: check if Breakpoint 2 is pending.
 -PASS: gdb.base/sym-file.exp: check if Breakpoint 3 is pending.
 +PASS: gdb.base/sym-file.exp: breakpoint at foo is pending
 +PASS: gdb.base/sym-file.exp: breakpoint at bar is pending

gdb/testsuite/
2014-04-15  Pedro Alves <palves@redhat.com>

	* gdb.base/sym-file.exp: Remove regex characters from test
	message.  Don't refer to breakpoint numbers in test messages.