Added gdb-remote program counter check at breakpoint.

Modified the breakpoint stop and start check to verify the program
counter printed immediately after stopping does match the breakpoint
address. This is based on a conversation with Greg Clayton clarifying
that the breakpoint stop handling code on a remote should do any and
all adjusting of the program counter at stop time, not at resume time.

Added a qProcessInfo parser and helper methods to add the collection
send/response elements to the packet flow. Removed the older pid-only
query mechanism. The parser verifies all the keys provided are within
the documented known set of key-value pairs.

Added helper routine to unpack the hex value of a $p-style register
read response according to the endian-ness of the inferior as reported
by qProcessInfo.

Added a test to verify qProcessInfo includes an endian key/value pair.

Refactored several older tests to move to the less verbose test
startup code. Most of these were the tests using the older
qProcessInfo pid-only retrieval code.