Building ipmitool with UBSAN and I got:
```
...
xxx/ipmitool/include/ipmitool/helper.h:191:14: runtime error: left shift of 160
by 24 places cannot be represented in type 'int'
    #0 0x55bddaa56f11 in ipmi32toh
       xxx/ipmitool/include/ipmitool/helper.h:191:14
```

Tested: with this, I tested ipmitool again and the issue disappeared.

Resolved: ipmitool/ipmitool#352
Signed-off-by: Tom Tung <shes050117@gmail.com>

Some of the header guard names in ipmitool duplicated with the ones in
freeipmi.

* ipmitool/ipmi_fru.h and freeipmi/fru/ipmi-fru.h both uses IPMI_FRU_H
* ipmitool/ipmi_sdr.h and freeipmi/sdr/ipmi-sdr.h both uses IPMI_SDR_H
* ipmitool/ipmi_sel.h and freeipmi/sel/ipmi-sel.h both uses IPMI_SEL_H

This is problematic as including the 1st will prevent the 2nd from being
included, leading to the loss of any declarations, inline definitions,
or other "#includes" in the 2nd header.

For example, including ipmitool/ipmi_sel.h and freeipmi/freeipmi.h fails
to build.

$ cat test.c
 #include <ipmitool/ipmi_sel.h>
 #include <freeipmi/freeipmi.h>
$ gcc test.c -I${HOME}/src/oss/ipmitool/include
In file included from /usr/include/freeipmi/freeipmi.h:90,
                 from test.c:2:
/usr/include/freeipmi/sdr/oem/ipmi-sdr-oem-intel-node-manager.h:48:44: error: unknown type name 'ipmi_sdr_ctx_t'; did you mean 'ipmi_fru_ctx_t'?
   48 | int ipmi_sdr_oem_parse_intel_node_manager (ipmi_sdr_ctx_t ctx,
      |                                            ^~~~~~~~~~~~~~
      |                                            ipmi_fru_ctx_t

Remove header guards and use "#pragma once" instead. In this way, we
don't have to do manual management to avoid name clashes.
* src/plugins/lan/md5.h is left as is being an external header
  originally.
* src/plugins/imb/imbapi.h is a convoluted header consisting of multiple
  header guards. Let's just add "#pragma once" and leave header guards
  as is for now.

Signed-off-by: Bing-Hua Wang <binghuawang@ami.com>

If a manufacturer's IANA PEN (aka manufacturer ID) was above
65535, it wasn't reported properly. Luckily there are no such
IDs so far, the biggest is 54077 as of 2019/06/18.

There is, however, an ID 0xFFFFFE used by fake_ipmistack
for debug purposes, and it was not reported correctly.

This commit expands the value argument to string searching functions
from 16-bit to 32-bit to allow for any possible IANA PEN.

Fixes: 73d6af57827fc85e78c700ca1dff00b3dbc63948
Signed-off-by: Alexander Amelkin <alexander@amelkin.msk.ru>

Some commands may return command-specific completion codes.
Now they are all reported as 'Unknown'.
Add helper functions to support such command-specific codes.
Command handlers will need to define their own valstr arrays
with completion code descriptions and then use specific_val2str()
instead of generic val2str() to convert the completion code into
a string.

Also reduce code duplication in helper.c

Signed-off-by: Alexander Amelkin <alexander@amelkin.msk.ru>

The function converts a host 32-bit integer into an IPMI
24-bit value (LSB first).

Signed-off-by: Alexander Amelkin <alexander@amelkin.msk.ru>

The function converts a set of command line arguments representing
byte values into a byte buffer and verifies each individual value
to be a valid data byte.

Signed-off-by: Alexander Amelkin <alexander@amelkin.msk.ru>

Make the argument to free_n() compatible with any pointers,
thus reducing the number of compilation warnings.

End-user-impact: None
Signed-off-by: Alexander Amelkin <alexander@amelkin.msk.ru>

free_n() will free the memory and clear the pointer, which will reduce
the probability a developer will forget to clear the pointer after
freeing.

Resolves: #79

Signed-off-by: Patrick Venture <venture@google.com>

Implement __UNUSED__ macro for marking symbols unused safely.

Partially resolves ipmitool/ipmitool#13

Signed-off-by: Patrick Venture <venture@google.com>

Make val in valstr 32-bit to accomodate the values added
by commit 329ebdff.

Signed-off-by: Alexander Amelkin <alexander@amelkin.msk.ru>