[MWF] Use full width for measuring text

Previously we applied the padding twice.
[MWF] Use full available height for text

This is especially relevant if we have to shrink the width because of
padding. In this case it is possible that MeasureString calculated that
the string would fit in one line, but because of padding we reduce the
width. If the button is large enough we want to display additional lines
even if MeasureString told us we only need one line.
[jit] Fix -O=precomp option to skip generic methods and not crash.
[io-layer] Remove more dead process code, add comments.
[io-layer] Make _wapi_shm_enabled () inline so more code can be optimized away if shared handles are disabled.
[bcl] Add an AppDomain.DoUnhandledException () internal method which can be used to invoke the UnhandledException event handlers.
Fix a warning.
Fix a warning.
Fix a warning.
[runtime] Don't define ucontext_t for android if PLATFORM is not android.
Implement the ReadEntityBodyMode properties
Implement Request.Abort()
Merge pull request #1353 from martinjt/ReadEntityBodyMode

Implement the ReadEntityBodyMode properties
Merge pull request #1354 from martinjt/RequestAbort

Implement Request.Abort()
Removed erroneously added property to HttpRequestBase in pull #1353
[sgen] Fix allowance calculation.

The formula for calculating allowance was not only overly complicated
but completely broken, which resulted in the allowance always being the
minimum (4 times the nursery size).  That resulted in too frequent garbage
collections when the heap grew larger.

Now we do something very similar to what Boehm does: Allow the heap
to grow by a third before the next major collection happens.
[runtime] Clean up the signal handling code by moving the signal handler signature definitions to mono-signal-handler.h and using them everywhere.
Fix a typo.
[jit] Remove some unused definitions.
Fix the build after the signals changes.