Bug 1076649 - Remove the '+' prefixing from mach commands with allow_all_arguments=True. r=gps

The reason to use '+' prefixing was to distinguish between options to the
mach command itself, and options that are passed down to whatever the
command does (like mach run passing down args to the built application).
That makes things unnecessarily awkward, and quite non-standard.

Instead, use standard '-' prefixing, and pass all the unknown arguments
down. If there is overlap between the known arguments and arguments supported
by the underlying tool (like -remote when using mach run), it is possible to
use '--' to mark all following arguments as being targetted at the underlying
tool.

For instance:
    mach run -- -remote something
would run
    firefox -remote something
while
    mach run -remote something
would run
    firefox something

As allow_all_arguments is redundant with the presence of a argparse.REMAINDER
CommandArgument, allow_all_arguments is removed. The only mach command with a
argparse.REMAINDER CommandArgument without allow_all_arguments was "mach dmd",
and it did so because it didn't want to use '+' prefixes.
Bug 1077384 - Make libmozglue a pseudo-LD_PRELOAD on android. r=nfroyd

In order to avoid adding more dlsym overhead than there already is, resolve
symbols directly in the library containing the linker. (GetSymbolPtr is
essentially free ; dlsym makes the system linker compule a ElfHash itself,
and that's quite expensive to do on all symbols)

This also paves the way for direct symbol resolution in all system libraries.