eval.c: reverse minsym and sym

eval.c: reverse minsym and sym

I noticed that in evaluate_funcall, where we handle
OP_VAR_MSYM_VALUE/OP_VAR_VALUE to figure out the symbol's name gets
the minimal_symbol/symbol backwards.  Happens to be harmless in
practice because the symbol name is recorded in the common initial
sequence (in the general_symbol_info field).

gdb/ChangeLog:
2018-03-25  Pedro Alves  <palves@redhat.com>

	* eval.c (evaluate_funcall): Swap OP_VAR_MSYM_VALUE/OP_VAR_VALUE
	if then/else bodies in var_func_name extraction.