Skip leading spaces when decoding hex values

[fjricci]

Summary

The StringExtractor functions using stroull will already
skip leading whitespace (ie GetU64). Make sure that the manual
hex parsing functions also skip leading whitespace.

This is important for members of the gdb protocol which are defined
as using whitespace separators (ie qfThreadInfo, qC, etc). While
lldb-server does not use the whitespace separators, gdb-remotes
should work if they do, as the whitespace is defined by the gdb-remote
protocol.

lldb/trunk/source/Utility/StringExtractor.cpp

 // by this function
 //
 // If there is not a pair of valid hex digits at the head of the
 // StringExtractor, it is left unchanged and -1 is returned
 //----------------------------------------------------------------------
 int
 StringExtractor::DecodeHexU8()
 {
+    SkipSpaces();
     if (GetBytesLeft() < 2)
     {
         return -1;
     }
     const int hi_nibble = xdigit_to_sint(m_packet[m_index]);
     const int lo_nibble = xdigit_to_sint(m_packet[m_index+1]);
     if (hi_nibble == -1 || lo_nibble == -1)
     {

 
 
 uint32_t
 StringExtractor::GetHexMaxU32 (bool little_endian, uint32_t fail_value)
 {
     uint32_t result = 0;
     uint32_t nibble_count = 0;
 
+    SkipSpaces();
     if (little_endian)
     {
         uint32_t shift_amount = 0;
         while (m_index < m_packet.size() && ::isxdigit (m_packet[m_index]))
         {
             // Make sure we don't exceed the size of a uint32_t...
             if (nibble_count >= (sizeof(uint32_t) * 2))
             {

 }
 
 uint64_t
 StringExtractor::GetHexMaxU64 (bool little_endian, uint64_t fail_value)
 {
     uint64_t result = 0;
     uint32_t nibble_count = 0;
 
+    SkipSpaces();
     if (little_endian)
     {
         uint32_t shift_amount = 0;
         while (m_index < m_packet.size() && ::isxdigit (m_packet[m_index]))
         {
             // Make sure we don't exceed the size of a uint64_t...
             if (nibble_count >= (sizeof(uint64_t) * 2))
             {