Add support for runtime selection of float ABI

tcc-doc.texi

@@ -176,6 +176,9 @@ In a script, it gives the following header:
 #!/usr/local/bin/tcc -run -L/usr/X11R6/lib -lX11
 @end example
 
+@item -mfloat-abi (ARM only)
+Select the float ABI. Possible values: @code{softfp} and @code{hard}
+
 @item -dumpversion
 Print only the compiler version and nothing else.