The biggest problem with this approach is that so many developers do it that if you use a third-party library you are likely to end up with a symbol name conflict, or multiple names for the same types. It would be wise where necessary to stick to the standard implementation provided by C99's stdint.h.
If your compiler does not provide this header (as for example VC++), then create one that conforms to that standard. One for VC++ for example can be found at http://msinttypes.googlecode.com/svn/trunk/stdint.h
In your example I can see little point for defining size specific floating-point types, since these are usually tightly coupled to the FP hardware of the target and the representation used. Also the range and precision of a floating point value is determined by the combination of exponent width and significant width, so the overall width alone does not tell you much, or guarantee compatibility across platforms. With respect to single and double precision, there is far less variability across platforms, most of which use IEEE-754 representations. On some 8 bit compilers float and double are both 32-bit, while long double on x86 GCC is 80 bits, but only 64 bits in VC++. The x86 FPU supports 80 bits in hardware (2).