GDB 7.7 for Android debugging

Win32 binaries of gdb-7.7 which I've built to work around Android issue 78239: gdb 7.6 resolves symbols very slowly in C++ stack frames.

Unlike Google's build, my build lacks Python support but has libiconv (i.e. set host-charset, target-charset and target-wide-charset) support.

To install:

1. Copy libiconv-2.dll to $NDK\prebuilt\windows-x86_64\bin\libiconv-2.dll
2. Copy gdb.exe to $NDK\toolchains\arm-linux-androideabi-4.8\prebuilt\windows-x86_64\bin\arm-linux-androideabi-gdb-orig.exe
3. Copy gdb.exe to $NDK\toolchains\arm-linux-androideabi-4.9\prebuilt\windows-x86_64\bin\arm-linux-androideabi-gdb-orig.exe
4. Copy gdbserver to $NDK\prebuilt\android-arm\gdbserver\gdbserver

To build from sources:

1. Install MinGW32 packages mingw32-base, mingw32-gcc-g++ (required by expat), msys-bison (required by gdb) and libiconv-dev (used by gdb)
2. mount c:/mingw /mingw
3. Build expat:
   1. Download expat (in my case, it was 2.1.0)
   2. tar xzfv expat-2.1.0.tar.gz && cd expat-2.1.0 && ./configure --prefix=/mingw && make && make install
4. Build gdb:
   1. Clone Android gdb from https://android.googlesource.com/toolchain/gdb.git
   2. cd gdb/gdb-7.7 && ./configure --prefix=/mingw --target=arm-linux-androideabi && make