awk: simplify tests for operation class

Usually, an operation class has only one possible value of "info" word.
In this case, just compare the entire info word, do not bother
to mask OPCLSMASK bits.

(Example where this is not the case: OC_REPLACE for "<op>=")

function                                             old     new   delta
mk_splitter                                          106     100      -6
chain_group                                          616     610      -6
nextarg                                               40      32      -8
exec_builtin                                        1157    1149      -8
as_regex                                             111     103      -8
awk_split                                            553     543     -10
parse_expr                                           948     936     -12
awk_getline                                          656     642     -14
evaluate                                            3387    3343     -44
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/9 up/down: 0/-116)           Total: -116 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
1 file changed