10335 mdb: fix fpcw2str()
The implementation of fpcw2str() (both in usr/src/cmd/mdb/intel/mdb/proc_amd64dep.c and in usr/src/cmd/mdb/intel/mdb/proc_ia32dep.c) has multiple problems:

FPPC, FPRC and FPIC macro constants should be used as bitfield masks, meaningless to print those out because the masked bits aren't simple yes-no values
To decode precision, rounding and infinity options, cw should be masked with the corresponding bit-mask first, then use equality check instead of bitwise &.

This bug has been found during the review of #10132: smatch fixes for MDB.

Build, install and run.
Example output before the patch:
root@openindiana:~# uname -snrvmapioX
SunOS openindiana 5.11 illumos-bc586359b7 i86pc i386 i86pc illumosSystem = SunOS
Node = openindiana
Release = 5.11
KernelID = illumos-bc586359b7
Machine = i86pc
BusType = <unknown>
Serial = <unknown>
Users = <unknown>
OEM# = 0
Origin# = 1
NumCPU = 2

root@openindiana:~# ps aux 2611
USER       PID %CPU %MEM   SZ  RSS TT       S    START  TIME COMMAND
root      2611  0.0  0.1 9756 1876 ?        S 23:56:50  0:00 /usr/lib/ssh/sshd
root@openindiana:~# mdb -p 2611
Loading modules: [ ld.so.1 libc.so.1 libuutil.so.1 libnvpair.so.1 libavl.so.1 ]
> ::fpregs
AMD64 (80486 chip with SSE)
cw     0x133f (IM|DM|ZM|OM|UM|PM|PC|IC|SIG53|SIG64|RTN|A)
sw     0x0000 (TOP=0t0) (0)
xcp sw 0x0000 (0)

fop    0x0
rip    0x0
rdp    0x0

%st0   0x0000.0000000000000000 = +0.0000000000000000e+00 empty
%st1   0x0000.0000000000000000 = +0.0000000000000000e+00 empty
%st2   0x0000.0000000000000000 = +0.0000000000000000e+00 empty
%st3   0x0000.0000000000000000 = +0.0000000000000000e+00 empty
%st4   0x0000.0000000000000000 = +0.0000000000000000e+00 empty
%st5   0x0000.0000000000000000 = +0.0000000000000000e+00 empty
%st6   0x0000.0000000000000000 = +0.0000000000000000e+00 empty
%st7   0x0000.0000000000000000 = +0.0000000000000000e+00 empty

mxcsr  0x1f80 (IM|DM|ZM|OM|UM|PM|RTN)
xcp    0x0000 (RTN)

%xmm0  0x00000000000000000000000000000000
%xmm1  0x00ffffffffffffffffffffffffffffff
%xmm2  0x0074736570616475422f65706f727545
%xmm3  0x6c75727869736f70002f6f666e69656e
%xmm4  0x00000000000000000000000000000000
%xmm5  0x00000000000000000000000000000000
%xmm6  0x00000000000000000000000000000000
%xmm7  0x00000000000000000000000000000000
> $q

root@openindiana:~# 

Note: |SIG53 and |SIG64 can't be present at the same time!
After the patch:
root@openindiana:~# uname -snrvmapioX
SunOS openindiana 5.11 master-0-g92c1a61163 i86pc i386 i86pc illumosSystem = SunOS
Node = openindiana
Release = 5.11
KernelID = master-0-g92c1a61163
Machine = i86pc
BusType = <unknown>
Serial = <unknown>
Users = <unknown>
OEM# = 0
Origin# = 1
NumCPU = 2

root@openindiana:~# ps aux 101174
USER        PID %CPU %MEM   SZ  RSS TT       S    START  TIME COMMAND
root     101174  0.0  0.1 9796 1840 ?        S 06:52:31  0:00 /usr/lib/ssh/sshd
root@openindiana:~# mdb -p 101174
Loading modules: [ ld.so.1 libc.so.1 libuutil.so.1 libnvpair.so.1 libavl.so.1 ]
> ::fpregs
AMD64 (80486 chip with SSE)
cw     0x133f (IM|DM|ZM|OM|UM|PM|SIG64|RTN|A)
sw     0x0000 (TOP=0t0) (0)
xcp sw 0x0000 (0)

fop    0x0
rip    0x0
rdp    0x0

%st0   0x0000.0000000000000000 = +0.0000000000000000e+00 empty
%st1   0x0000.0000000000000000 = +0.0000000000000000e+00 empty
%st2   0x0000.0000000000000000 = +0.0000000000000000e+00 empty
%st3   0x0000.0000000000000000 = +0.0000000000000000e+00 empty
%st4   0x0000.0000000000000000 = +0.0000000000000000e+00 empty
%st5   0x0000.0000000000000000 = +0.0000000000000000e+00 empty
%st6   0x0000.0000000000000000 = +0.0000000000000000e+00 empty
%st7   0x0000.0000000000000000 = +0.0000000000000000e+00 empty

mxcsr  0x1f80 (IM|DM|ZM|OM|UM|PM|RTN)
xcp    0x0000 (RTN)

%xmm0  0x00000000000000000000000000000000
%xmm1  0x00ffffffffffffffffffffffffffffff
%xmm2  0x0074736570616475422f65706f727545
%xmm3  0x652f0073656c75727869736f70002f6f
%xmm4  0x00000000000000000000000000000000
%xmm5  0x00000000000000000000000000000000
%xmm6  0x00000000000000000000000000000000
%xmm7  0x00000000000000000000000000000000
> $q

root@openindiana:~#