rename glesv2 functions, load some of them dynamically

the dynamically loaded ones are those that conflict with GLESv1.
allow gles+gles2 linking at the same time (v3)

Compile both GLESv1 and GLESv2 hooks at the same time, load symbols
that intersect between GLESv1 and GLESv2 dynamically on GLESv2 side
from correct lib. There is still possibility to compile GLESv1 or
GLESv2-only version by modifying the makefile.

Osmos is linked to both libGLESv1_CM.so and libGLESv2.so and
uses symbols from both, so old GLES=x way was not enough.
Merge pull request #24 from notaz/multigles

allow gles+gles2 linking at the same time (v3)