Fix for most Xcode/clang warnings on OSX

[floooh]

This PR fixes the following warnings when compiled with latest clang in Xcode7 on OSX 10.11, there are 2 warnings remaining which I need advice on how to fix (see below).

The tests are running successfully.

In file included from /Users/floh/projects/glslang/SPIRV/SPVRemapper.cpp:37:
/Users/floh/projects/glslang/SPIRV/doc.h:217:9: warning: field 'resultPresent' will be initialized after field 'opDesc' [-Wreorder]
        resultPresent(true),       // most normal, only exceptions have to be spelled out

/Users/floh/projects/glslang/SPIRV/SpvBuilder.cpp:1217:5: warning: variable 'resultType' is used uninitialized whenever switch default is taken [-Wsometimes-uninitialized]
    default:
    ^~~~~~~
/Users/floh/projects/glslang/SPIRV/SpvBuilder.cpp:1221:57: note: uninitialized use occurs here
    Instruction* query = new Instruction(getUniqueId(), resultType, opCode);
                                                        ^~~~~~~~~~
/Users/floh/projects/glslang/SPIRV/SpvBuilder.cpp:1178:18: note: initialize the variable 'resultType' to silence this warning
    Id resultType;
                 ^
                  = 0

In file included from /Users/floh/projects/glslang/SPIRV/disassemble.cpp:53:
/Users/floh/projects/glslang/SPIRV/doc.h:217:9: warning: field 'resultPresent' will be initialized after field 'opDesc' [-Wreorder]
        resultPresent(true),       // most normal, only exceptions have to be spelled out

/Users/floh/projects/glslang/glslang/MachineIndependent/Initialize.cpp:1057:31: warning: '&&' within '||' [-Wlogical-op-parentheses]
    if (profile != EEsProfile && version >= 150 || esBarrier)
        ~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~ ~~
/Users/floh/projects/glslang/glslang/MachineIndependent/Initialize.cpp:1057:31: note: place parentheses around the '&&' expression to silence this warning
    if (profile != EEsProfile && version >= 150 || esBarrier)
                              ^
        (                                      )


In file included from /Users/floh/projects/glslang/glslang/MachineIndependent/ParseHelper.cpp:44:
/Users/floh/projects/glslang/glslang/MachineIndependent/preprocessor/PpContext.h:89:28: warning: field 'ival' will be initialized after field 'space' [-Wreorder]
    TPpToken() : token(0), ival(0), space(false), dval(0.0), atom(0)

/Users/floh/projects/glslang/glslang/MachineIndependent/Scan.cpp:688:48: warning: '&&' within '||' [-Wlogical-op-parentheses]
        if (parseContext.profile == EEsProfile && parseContext.version >= 310 ||
            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~
/Users/floh/projects/glslang/glslang/MachineIndependent/Scan.cpp:688:48: note: place parentheses around the '&&' expression to silence this warning
        if (parseContext.profile == EEsProfile && parseContext.version >= 310 ||
                                               ^
            (                                                                )

/Users/floh/projects/glslang/glslang/MachineIndependent/Versions.cpp:455:17: warning: enumeration values 'EBhMissing', 'EBhDisable', and 'EBhDisablePartial' not handled in switch [-Wswitch]
        switch (getExtensionBehavior(extensions[i])) {
                ^

There are 2 warnings remaining, these happen because a constant 0xFFFFFFFF is compared against an enum which doesn't contain such a value. To fix this I would need advice what your preferred fix would be, for instance, adding an 'Invalid' entry to the enum which has value 0xFFFFFFFF, or performing a cast of the enum to unsigned int inside the if()...?

/Users/floh/projects/glslang/SPIRV/GlslangToSpv.cpp:2446:13: warning: comparison of constant 4294967295 with expression of type 'spv::Decoration' is always true [-Wtautological-constant-out-of-range-compare]
    if (dec != spv::BadValue)
        ~~~ ^  ~~~~~~~~~~~~~
/Users/floh/projects/glslang/SPIRV/GlslangToSpv.cpp:2452:13: warning: comparison of constant 4294967295 with expression of type 'spv::Decoration' is always true [-Wtautological-constant-out-of-range-compare]
    if (dec != spv::BadValue)
        ~~~ ^  ~~~~~~~~~~~~~

[mre4ce]

This warning still exists when compiling on Linux as well:

GlslangToSpv.cpp:1973:33: warning: comparison of constant 4294967295 with expression of type 'spv::BuiltIn' is always true [-Wtautological-constant-out-of-range-compare]
                if (builtIn != spv::BadValue)
                    ~~~~~~~ ^  ~~~~~~~~~~~~~

This is not just a warning but a potential bug. The underlying type of an unscoped enum is an implementation-defined integral type capable of representing all values of the enum.

Considering that spv::Builtin only represent a limit number of enum values the underlying type could be 16-bit or even 8-bit in which case the comparison to 0xFFFFFFFF (spv::BadValue) will always be false.